i agree with what katy's saying about the threats. i can't begin to imagine how difficult this situation must be for both you and him. but it's possible for him to learn what dysphoria is and what the different moods are, and then learn how to act while in them.
i don't have bipolar, so i don't know as well as katy what the best techniques are. but i do have different moods, moods that don't feel like myself, and dealing with the different moods is kind of like learning how to run in different terrains...running in sand or snow, running underwater, running uphill, running on nice short grass, running downhill (whoaaa!) and i've learned what they all feel like, and, while they do affect me and my actions, i am so much better now at keeping my balance through them. one can't act the SAME through every mood, just like you don't really run the same if you are running in sand...you learn to move your legs in a different way that makes the best of it...you learn to make your reaction to these moods a reaction that actually helps balance things out, rather than adding more struggle or grief to what the illness is already putting forth.
does that make any sense at all?
but the severity is different for different folks. what makes sense to me and my depression may seem kinda flippant and superficial to someone with a more severe situation on their hands, yknow?
i know you've talked a little about his physical activities, that he was taking tennis, etc... does he still do that? for me, i've learned a lot about what to do from very physical experiences. it's hard to explain, but i can tell what kind of mood is going on from certain ways i feel in my body. and physical activity isn't just good for getting aggression out, i think it's been good for helping me be aware of my body, and learning physical ways of "keeping balance" that i can then reuse mentally.
anyways... i guess i'm saying, he needs to acknowledge that he IS feeling all firey and ragey, and maybe that's where the lashing out STARTS... but it's all actions that are adding fuel to the fire. my GUESS (and i stress guess, lol, since i'm not expert) is that he needs to learn ways of screaming "i'm angry and don't feel like myself and i feel all firey and mad and want to hurt everybody!!" that don't get everyone else all worked up as well. (that, and also learn some things like "okay, i'm feeling mad and angry and want to hurt everyone... what can i do that would really make me feel better?") i'm guessing that other folks' reactions just give him more reason (in his mind) to get madder.
if i've said any of that stuff before, and sound like someone goin on and on about myself, i'm sorry! lol! not being a parent, i can only talk about me. 
and when i put what i do in words, it does sound kinda silly
"HELLO I'M TACTILE !" is an anagram of my name
, that is an ill-KS. 
When I am ill like that I can argue red is blue. 
it may help him to know that you have emotions too, and his own crying and getting angry, while they need to be kept within bounds, aren't some kind of freakish thing in themselves. also, you may be stressing yourself out if you feel you must be stoic all the time.
