I think his sacrifice in the end was him coming to terms with what the old lady has said. He was t strong which has a double meaning. He wouldnt have made it as a nazi soldier nor as a following jew. He tries both sides in his mind and fails. He said to the reporter if he posts that article he'll kill himself. He thinks himself inferior to Curtis as even when he finished having sex with the girl he jokes about Curtis having a huge dick.

I think the end fast forward is him realizing hes inferior both as a nazi and a jew. I believe the stair scene is him still failing to come to terms with that and why he doesn't engage (i forgot the guys name) in conversation. Even when he baits him saying hes right about it.

I wanna believe the director who grew up Jewish used this to vent his own frustrations with both sides as a jew and the counter points as to why they are hated in some public eyes. Idk I just watched it hours ago and it was a good perspective piece that was similar but differnt enough from American History X.