I would request a transfer now, due to threatening behavior by roommate. Odds are a room will be available next spring at the latest (there may be a room available now). The “rage” thing is what I would key on … .that is not normal. And 9 of 10 is a serious concern.
The RA is likely a mandatory reporter and you have already contacted several people. It would seem the next step is for the roommate to be nudged into counseling, but I would want my child away from this kid first, it may trigger severe rage to find out he has been reported on.
The RA should also be reporting on any observations by other residents. And, if you know last years roommates, there may have been some non-trivial issues last year too, possibly even some altercations, which would just strengthen the case for moving this kid or moving your kid, now.
Mental health issues really need trained personnel to get involved, since seemingly innocent comments or attempts to help could cause either aggression or depression (ranging to potential self-harm).
Kid needs counseling, but your child does not have to be involved for a full year. Even smaller roommate conflicts have a way of getting worse not better …
In the meantime, have you son identify a place to stay overnight if his roommate acts irrational or threatening, if he has a friend lined up he can just go with a few items and not have to sleep with one eye open…