omg does j!sam time travel again after j!dream kills him? or if not what happens after?

He does not! Though we have briefly discussed a time loop AU where he does, where the loop resets when Sam dies or Dream dies.

In JMAH ,, he just has to ,,, move on. He's back at the beginning--alone in his base thinking over the last year, down a life and many months that he'll never get back, and Dream is free.

There's some measure of regret--things that he could've done better, been more careful about tommy and quackity, dealing with that more swiftly before they could interfere. There's a lot of anger--he had made things better! For everyone! He's the only one that knew about how badly that first timeline had gone, and he'd done so much to fix it, and now they've ruined everything again and for what! There's still some more woe-is-meisms--he's suffered so much, silently, without complaint, and now everything is ruined again. All his efforts laid to waste.

And...most complicated of all, there's a measure of satisfaction. He did change things. Dream was better behaved. Maybe his task was doomed from the beginning...but he did make things better in the end, didn't he? He did his best.