I understand sometimes patterns are hard to get out of. I am still working on some. I just wanted to stop by and remind you that you don't have to fear him. You always did fear his reactions, because yes, they are off the wall. But now, he has zero control over you.
In CA, a 14 year old will be heard and will be heavily considered regarding where he wants to live. 14 is kind of an arbitrary number, because the courts will hear a 12 year old too, if there is really good reasoning. Your one son may live with you full time, and your younger one should really be having an input. There is certainly obvious reasoning as to why your kid should have say, because your ex has done some nutty stuff. Have you talked to your younger son yet about what he sees as the best case custody schedule.
As for child support and 50/50 custody. With 50/50, the higher earner will still pay. Salary is considered in the equation.
It is something to navigate, negotiate and not have a decision be made this minute. And if those kids don't want to go over there right now, they don't have to. And with your kids ages and your ex's instability, I would not be pushing the kids to do anything they don't feel comfortable with right now. Let them decide until you guys have something hammered out.