Yes, there is a dimension for every event. Literally EVERY event. Infinite universes.
When you travel between dimensions, you are destroyed in one dimension and your atoms are reassembled in the one you're going to. Would your memories last? Maybe, maybe not.
I think the thought behind combusted timelines was that eventually you can split a timeline to the point where it becomes fundamentally unstable. It would probably affect the whole timeline and not just the offshoot.
No, you wouldn't, because there would still only be one you per timeline. You show up, kill your Timeline A self, get rid of the body and there you go. Unless multiple versions of you are going to jump ship to your particular timeline, you should be fine.
I have never taken a physics course, so if anyone has, the floor is yours.
Whatever, right? It's your story, and you decide what you want to put up and take down.