No, he either exists or doesn't. He is only in one position in time and space.
If he never existed at all then he can't be aborted, if he does exist then he wasn't aborted.
Not sure how to describe the premise in a way that would adequately explain it. The film rejects the notion of Many Worlds, there can be only one outcome, the timestream doesn’t split - it merely mends itself (within reason - Doc does warn Marty about excessive interference). As you say, Marty can only exist in one place in space and time. However, he is in a superposition state specifically because of his interference, and he can either completely vanish or continue to exist depending on what actions he undertakes. In that sense, he is, but simultaneously isn’t - his state is uncertain until he guarantees his own existence.
We’re observers looking at this situation from outside of the universe of the movie. Marty’s timestream will correct itself to avoid paradox, but that won’t affect our memory of Marty because we don’t inhabit his universe. To us, he’ll suddenly vanish because he’ll accidentally prevent his birth. As far as we’re concerned, he’ll be an entity that existed and suddenly ceased to exist. “Getting aborted from time” is as good of a description as any to the viewers, but I can understand how you’d find that objectionable since from the perspective of other inhabitant of Marty’s universe he’d simply never exist at all.
Never thought making a joke would take us to a discussion about quantum physics, but I always like when threads go in unexpected and interesting directions (within reason). I’m happy to agree to disagree on the applicability of the term - it’s not exactly a serious discussion anyway, we’re talking about a film. I am happy to see that so many people like it though, it’s a classic.
EDIT: tl;dr Marty can only exist if his parents get together. He screws up at the very beginning and starts the process of vanishing. He messed up “a little bit”, but not “quite enough” to fully disappear. As such, he doesn’t “exist” or “doesn’t exist”, he “maybe exists” until his fate is sealed. That’s an in-between state contingent on whether he reverts his screw-up or not.
Saying something you don't believe to make someone look stupid is not trolling?
I don’t think so, no. If you want to show that something is absurd, coming up with an example that demonstrates this absurdity is a good way of going about it. How else would you do it? We’ve had our fair share of absurd analogies in this very thread - I think they can be a valuable tool that takes us closer to the truth. Different strokes for different folks, I suppose.
