You said "the majority of the people who dedicate their life's work studying and thinking deeply about the big picture issues (origin of the universe, the nature of morality, free will, etc) are turning to atheism in droves". But we must be careful to not draw conclusions from unfounded inferences. What we know is that a large percentage of professional philosophers are atheists. What we don't know is whether this is because Christians who become professional philosophers convert to atheism when they become more knowledgeable. This may be a case of selection bias. People who are already atheists who want to think deeply about these issues have the choice of becoming a philosopher, but people who are already Christians who want to think deeply about these issues have the choices of becoming a philosopher, a priest, or to join one of many religious orders. If apologists and theologians were not included under "professional philosophers" in that study, then those were potential career options as well.
Another explanation for atheistic philosophers is that the places where philosophers learn, universities, are currently heavily secular, and are very often biased against Christianity specifically. Universities used to be heavily religious. Now, it's possible that this shift in the first place occurred because people became more knowledgeable, but did we really discover that many philosophical breakthroughs since 1850?
If something is false, one should not need to treat it with derision, and get people's feelings involved. It should be clear enough by itself.
It's also worth pointing out that 72% of philosophers of religion are Christians. Those who think deeply about religion specifically are mostly Christian. Now, this could be because of selection bias as well. But at the end of the day, something isn't true because smart people believe it; it's true because it is so in reality.
I wouldn't stake my belief solely on the first cause argument, since there are many proofs of God. But if I saw that reason did not show that God exists, then I certainly would change my beliefs. At the moment I am completely certain this will never happen, as I have found many, many convincing reasons for God's existence, and have yet to find one convincing reason against God's existence. But God is Truth. To obey God, I must never shy away from the Truth for any reason. To do so would be a contradiction.
You said that the existence of a first cause was logically necessary, but not the attributes of that first cause. So you believe that it is logically necessary that a first cause has to exist, but that first cause could have logically been different and still would have worked as the first cause.
This is the crux of where we disagree on logical necessity - so let's solve it.
What holds the first cause in existence? Necessarily, itself. So, how could the laws of physics hold themselves in existence? For something to hold itself in existence, it has to exist by its very nature. Doesn't something that exists by its very nature have to be defined as something which we cannot logically imagine could possibly be different? But the laws of physics we can logically imagine to be different; hence they can not exist by their very nature; therefore they cannot be the first cause.
It also seems rather arbitrary to me to apply self-existence to the laws of physics. What is different about the laws of physics that makes them a suitable candidate for self-existence?
I am certainly not arguing we should believe in anything that we have no reason to believe. But we should be careful not to rely too heavily on science when the first cause may very well be a truth only reachable through philosophy, not science - if it exists outside of physical existence.
If "I" only meant thought and memories, then how would "you" be here to observe them? A computer can have things very similar to thoughts and memories, but the difference between you and a computer is an "I". An "I" is consciousness. I argue that no concept is less abstract. An "I" is, in fact, what we can be most certain of; and what we subconsciously are always most certain of. Every human knows at heart before all else that "I think, therefore I am".
Simple-minded doesn't mean indivisibly minded, but it does mean a mind that has less intelligent thoughts, or thoughts that are made of fewer logical parts. When we say "chess is a complex game" we mean because it has many rules and many different strategies. Tic-tac-toe is simple because it has few rules and few strategies. More parts = complex. Less parts = simple. Perfectly simple would then be indivisible. A turtle's brain is simpler than a human's. Whether a turtle has a mind, or a consciousness, I do not know. A turtle may be only a collection of physical responses, like a sleeping human (though without a dormant consciousness). If a turtle does have a mind, that mind is equally as simple as a human's. The turtle's mind, if it exists, lacks the ability to reason, which humans have. So a human mind has more abilities than a turtle's mind might have. But an ability is an attribute of a thing, not a part of a thing. A different way of looking at something. So a chair has both density and mass, but a chair is not composed of density and mass, and cannot be separated into the density parts of the chair and the mass parts of the chair. So with a mind. If a mind is then uniquely simple in its existence, would we expect a mind with more attributes than humans or fewer attributes than humans? If a mind was the first cause of the universe, then wouldn't it make the most sense for that mind to be more capable than ours and have more attributes?
There's a reason the victim's families would not be happy about a serial killer being "imprisoned" in a mansion. They believe in Justice.
Suffering is not the greatest evil. Moral evil is.
You don't believe in Justice, but you do believe in Mathematics. Is it nonsensical to say that Mathematics is inherent in God's nature? No, because you know Mathematics is true. I did not mean to use "Justice is inherent in God's nature" as a proof of Justice. The hypothetical serial killer was my proof. My point was that Justice is not necessary because of some sort of emotional satisfaction for God; it is necessary because it is true. And that truth is not external to God, but internal to God - though this fact is a clarification, and not a proof that it is true. So it has been always when I have said something was part of God's nature - I never meant such a statement to prove anything by simply being stated. I was attempting to explain fully what I believe - the proofs were elsewhere.
But I see you were not convinced by my proof of Justice by reductio ad absurdum via hypothetical serial killer. But Justice at a more fundamental level is the idea of people deserving good or bad according to what they do. But I assume you do still believe in Justice - that people do in fact deserve things? You believe a person deserves to get paid after a hard day's work, right? And deserves to not get paid after a day of skipping work? Likewise, heaven and hell. Saying that hell is immoral is equivalent to saying that it is unjust to not pay an employee who skips work. The consequences don't matter in the employee example - if the world was going to end tomorrow, it would still be just to not pay a worker who chose to not work (separated from any complicated consequences that come with a hypothetical world-ending scenario). You are arguing for a middle option, eternal unconsciousness or destruction. The middle option in the employee example might be to pay the employee who refrains from work half wages. This might very well be good and generous, but is to not do so unjust? Isn't it conceivable that a choice to not pay the wages of a worker who chooses to not work is, in a sense, more just than to pay them half wages? But, if God is all good, you may say, isn't God required to choose the more generous option? God is merciful, but God is also just. Justice is sometimes better than mercy, and though we may not be able to fully understand when this is, isn't it not contrary to reason that God can? At this point I am only aiming to prove that the existence of hell is not contrary to reason.
Those who freely choose to not seek the truth also therefore freely choose to not seek goodness, since to seek goodness one must first know what is good. One who freely chooses to not seek truth and therefore not seek goodness is freely choosing to not seek God. If someone chooses to default to what those around them believe (to base their beliefs on their desires; mainly their desire to fit in with those around them), then they are at fault, have chosen themselves instead of God, and may indeed go to hell.
Those who are very poor or who really do not have the time to seek the truth very much, but do what they can, are not in this category. We are never at fault for what we cannot choose.
Does this mean many are going to hell? We cannot know anything of the sort. We don't have the capability to look into someone else's mind and discover whether they are really seeking the truth or not. We especially cannot look into someone's mind to discover if they are seeking the truth at the hour of their death. We can only make guesses about others. The only place where we can and must judge the truth of this matter is within ourselves.