Biff doesn't become the richest man in the world by betting on sports;
It's funny (not) how much he resembles Rump.
it is not impossible, in a many worlds multiverse, to go back and kill Hitler,
Well it is impossible for ME. In a 'paradox' sense, Hitler is my grandfather.
Still not impossible. As I just described, in a many worlds multiverse, all possibilities have occurred, and changing "the past" is futile - because there is no "
the past". You can change as many pasts as you like, there will still be infinite presents and futures, including the one where you decided to change the past, and then did so.
My parents met during the war, while stationed in Washington. Without the war, I wouldn't exist.
I would guess, most of the world is in the same boat at this point.
A large bunch of people died, survived, moved around, had different jobs, met different people, had different mates ... than they would have otherwise, and had a baby boom. (and now grandkids)
Sure, even tiny differences in the past lead to widely different presents. That's no problem for my model though, because infinity is big enough to contain them all.
it just moves your personal perspective into a different timeline
Does it? Without real time travel to test, what timeline will your perspective move to, or return to?
Well, it's a model. Other models are available, but this is one of those in which the grandfather paradox is resolved (or rather simply doesn't exist).
Your original will be gone. Perhaps you could (or need to) just stay in the past.
Perhaps. If you can find a mechanism to prevent movement forward in time, that would be an amazing breakthrough though. It's essentially impossible to stay in the past; All of the stuff you did there has knock-on effects into the future (as you yourself just pointed out - Hitler is dead, but his effects on the universe are still evident, and you are one of them).
In a multiverse, there are also timelines where you didn't travel into the past. If you succeede and return, you may end up in one of those. So it would seem like no change (except there would be two of you).
Maybe. There's no paradox in that, though.
We are at a point in history similar to 1939. No need for time travel to do what needs to be done.
Every point in history is such a point. Unintended consequences are a real thing, though.
There's a massive
corpus of literature exploring this theme.
Steven Fry's
Making History posits a world in which disposing of Hitler leads to a Nazi victory in WWII, as his place is taken by someone equally evil, but actually
competent.
Flight 39, by Phillip P. Peters has the Allies win WWII by a negotiated peace in 1943, after Hitler's assassination. As a result, no atom bombs were developed until after the war, and the Cold War adversaries had no real examples of nuclear bombings of cities, to dissuade them from pressing the button and destroying the world. So they did just that.
Assassinations sometimes have the effects the assassins hope for; But they often don't. Killing Hitler seems like a no-brainer, but there are potential repercussions that could be even worse than what actually occurred - and the very real possibility that the upshot would be essentially no change at all.
Nazi Germany looks like it needed Hitler, but realistically, there were plenty of other top Nazis who might have done much the same things, had Hitler been removed. And they might well have done them more effectively. The focus on the centrality of Hitler himself is largely propaganda.
Get rid of an evil buffoon from the top job, and the risk is strong that an equally evil (but less buffoonish) person takes his place. Particularly if the removal involves an assassination, rather than due process such as an election, or an impeachment.
Assassinations create martyrs. And they lead to a groundswell of popular support for the ideals and political allies of the deceased.