There is no 'proper' definition of anything. That said, faith (i.e., thinking something is true without any reason to (no evidence, no rationale, etc)) is certainly a requirement for a belief system to be a religion.
You appear to be conflating
weak atheism with
strong atheism:
- Theism is the belief that deities exist
- Strong Atheism is the belief that deities don't exist
- Weak Atheism is where one holds neither of these beliefs
Weak Atheism is the logical stance to take, since there is neither evidence for or against the existence of deities. However, the universe looks exactly as we would expect it to look if deities don't exist. On those grounds alone, one could dismiss deities until evidence presents itself; after all, one is not deemed an irrational zealot for disbelieving in pink unicorns and the like.
Now, atheism itself is simply the logical conjugate to theism: theists say "I believe gods exist", atheists say "I don't believe gods exist". Strong atheists simply go one further than their 'weak' counterparts and say "I believe gods don't exist".
So atheism isn't a religion, since it isn't even a belief system: it is the
rejection of a belief system (namely, theism).
Don't be silly. Faith isn't some physical quantity that can exceed containers. It is simply a status of belief: you either have faith or your don't.
Not really, since Christianity makes
far more claims than even Strong Atheism. And what does "the reality of science" have to do with anything?