Not sure if this thread is still on topic after 47 pages, but I read the OP and have a few things to say:
A. Time
First, the way you describe time is a bit awkward. The reason why someone might say that time is "meaningless" before the big bang is that it would be measurable without context of something affected by time. Without time enacting on something, it's impossible to calculate, not that it is of little value or consequence.
Second, discussing whether time extends before the big bang and after the heat death of the universe is not restricted to a dichotomy of atheists thinking one way and religious thinking another. A religious person may argue that God and his heavenly plane existed before the universe, and thus time extends indefinitely before it; similarly, an atheist may argue that time begins at the point of the expansion due to our understanding of time. Saying, "I can't be an atheist because of dispute on something not tethered to belief in a God," is nonsensical.
B. "I'm not an atheist because I believe that [even] the most scientific modes of thought we will eventually hit a brick wall where unscientific "things" become necessary to explain.
You're setting yourself up for problems. This sort of thinking is what keeps people content in their current set of knowledge instead of expanding it to find new answers. In the same way that you may scorn an atheist for not believing that somehow, somewhere there could be a God, you are saying there is one because somehow, somewhere there may be something science can't explain. This is the ludicrous. Which brings me to my final point...
C. Real reasons to consider atheism
Don't worry about the metaphysical, that's a scientific dispute and not a theological one. If you want to say you can't be an atheist, you should provide reasoning for why you MUST believe in a god. If you illuminate the justification of your position, you not only show why you aren't an atheist but also provide a reason for others to believe. Rationalism is what I make decisions based off of: evidence instead of faith. If you too go by evidence, then the fact that the Bible is historically inaccurate, scientifically incorrect, morally questionable, repeatedly inconsistent, and anonymously authored would be strong reasons to doubt. The fact that believers of all faiths will say theirs is correct, that theirs prophets are true, and that they really talk to their god while the others religions really don't lends strong credence to the idea that none of them are honest. You could also talk about how few of the things promised in the Bible came true. You could look at pagan, Egyptian, and other ancient societies' astrology and compare the symbolism there to that of Christianity. There is absolutely no evidence to point to there being a god.
If evidence isn't your thing, I could appeal to your emotion and your conscience. How often are children brought to churches, mosques, synagogs, temples, etc. and indoctrinated since before they can walk to believe in god? How many parents are bigoted against "sinners" and people with lifestyles that don't align with the horrendous guidance the Bible provides and what of the people that suffer because of that? How often does god answer your prayers, especially the ones you really need, when you're begging on your knees, in tears? What about people that die while doing that? What about questioning the morality of a god that would create people knowing how things were going to turn out and let them happen; knowing who would be murdered, *****, killed by nature, cannibalized, mentally ill, still born, cancerous, diseased, sterile, criminally insane, etc. and doing nothing to stop it. What about a god who performs miracles to appear to some people some of the time to tell them trivial things while there are people waiting on miracles to help them with their starvation, amputated body parts, or other helpless situation? What about the morally bankrupt idea that when you do wrong to someone, that you can talk to a 3rd party and remove your guilt and be forgiven of your transgressions? How is there any responsibility to your fellow man with such an idea?
Finally, I'll approach you financially. If you believe regardless of evidence and morality, then I submit to you the impact the church has on the economy. The entire revenue pool of the church comes in the form of donations, tithes. How well a church does is dependent upon how much money the churchgoers are putting in the plates when they show up. The more people, more money. The more convicted, more money. If you can fill your pews and get them to put money in, then you've done your job. How do you do that? In order to maintain a church, you have to enlist people like any other company. You need custodians, cooks, teachers, deans, ministers, etc. Those that don't do work voluntarily will be getting paid. So you have your workforce created a welcoming environment where there is a place for everyone (children, teens, young adults, adults) to worship. These groups are taught to fear god, to hold his laws, etc. in order to propagate the atmosphere that either gilts people into donating or promises them something intangible in the future for a donation today. How well the machine does determines how much the church can expand, how many people can be enlisted in the work force, the number of programs used to draw more people in, community projects, etc. When all is said and done, the left over money, which is tax exempt, goes to the owner, usually the priest/head minister. The person that gets all the profits usually makes bank, usually. I have yet to see a poor church owner. Not to say churches and the people that run them see the monster this way or actually must operate this way, they see it as evangelical work, but the power of god comes in the form of the power of money. The more money you have, the more people your church can reach out to (I'm looking at you giant stadium churches with spots on TV and whatnot). The point is: the more successful a church is, the more money it's siphoning out of that community for the purpose of maintaining itself and give a little piece of it back for reputation. It's damaging.
Kinda shot this off the top of my head. Hope it isn't a boring read or something. I like ranting.