I’ll admit I was misinterpreting the OP. I thought the boyfriend had already been sentenced and the “might” and “up to” refered to the possibility of an early release.
Your advice is sound. He should get a good lawyer even if the trial is over. He’ll still want legal advice for the sentencing.
As for the OP’s decision about leaving him, that’s obviously her choice to make. But don’t leap into it just because of this. A court trial may seem like the biggest event of a lifetime and sixty days may seem like a long time but it really isn’t. This’ll pass. It’s true that sometimes a crisis can clarify an issue but more often a crisis just obscures the real issue behind the current emergency.
Well, I’m sorry you’re going through this. You sound like you’ve got it together very solidly, and your judgment sounds thoughtful. You’ll be OK. Remember to take care of yourself and your own stresses, and let yourself lean on the other supports in your life when you need to.