Sounds like depression to me. I went through something very similar when i had to drop out of college + go back home to pay the bills since my dad got laid off and mom became terminally ill. I don't know of anything that might help to get him out of that mind set besides a few good friends and his avoiding them now or driving them away now right? It's a big bottomless pit and it takes a lot to climb out of it.
But for your initial question, that is not a 'healthy' view of an istp, but rather in a bad mood. However, i've been called wacko more than once for my comical satire so yes, istp's can be crazy aswell. However even when i was down i never moved over to manipulation. I just -hate- people that do that. If i catch anyone trying that on me they will be sorry soon enough. It's a trait each one of us possess and especially those who love strategy and seeing how things tick / work out can excell in it. However, i wouldn't call it a 'typical ISTP trait' even tho we can excel at it.
Also, your initial assessment that his 'moodiness' comes from lack of understanding of feelings is partially accurate. He probably even doesn't know why he is so mad and infuriated and is in denial. Nothing can change that around, he has to realize it himself.