I agree with everything except the second point. What you say is true, but Leftists have proven themselves not to be counted on for turnout. A Democrat could expend all their energy chasing the Left, alienating a lot of centrists, and then one little thing starts making the rounds on Tiktok right before the election and y’all will abandon him. It doesn’t even have to be true. The GOP could make a doctored video of him saying the N-word, and the suspicion alone would drive away enough Leftists to cost him the election.
Centrist voters are dependable. Leftist voters are fickle. Add in the fact that there’s a LOT more centrist voters, and the calculus is obvious.
That said, I do think he blundered here. As you said, numbers on Israel are changing. Biden came down too hard on the side of Israel, not just morally but also politically.
Bidens best bet here was to be vague and noncommittal until Israel finally commits an atrocity covered enough by the media to tip a critical mass of centrists against Israel. Then Biden could suspend aid and be seen as a hero by all. He’s severely limited the chance of that happening now.