Life as an organic replicator seems as good a shorthand one as any, though even if a particular organism is incapable of replicating (some defect in its biology) that wouldn't make it not alive, would it?

The notion that professing to lack belief in something presupposes you had to believe in the existence of that to begin with (and moreover, that the object had to be real also) falls completely on its face.

But for those who could suffer backlash as a non-believer, you could answer in a way that is technically correct, something like, "I don't think I attend the church you do," smile, and change the subject to something less controversial, like politics.

What science can tell us is that all the observable universe dates back to around 13.8 billion years ago, and commenced in a burp when the matter/energy/spacetime we can see originated. But from what?

Civility is at heart being honest and kind.  Civility is not failing to call out ignorance, or hiding one's deep convictions, but how those are presented in public.

Everywhere. Now in most of the places on Earth it can still get you dangerously in trouble