hmm. i think if it was me, i would try to go and stay somewhere else for awhile...your son's perhaps?
it that is not possible, i would call the 800 number and see if they can offer you some assistance.
in the meantime, i would stop trying to control the situation, put on a good set of headphones and go about my day. i would no longer monitor husband's medical situation. i would not try to prevent grandson and husband from coming to blows. i would let them attack each other and then when it was over, i would call the police. this might be just what you need to get someone out of the house and in a jail cell so that you get some peace. they are grown men. it's their decision how they behave.
naive