Diagnose this mental illness?

[Dave]

So for my whole life I've watched my Dad throw massive temper tantrums over nothing. I'm not really sure how to classify it, as they seem completely random and have no origin. Randomly I'll say something to him, such as "Hey Dad, what's up?" and he'll yell at me and leave the house or just drive away for a little while. When he comes back he is in a perfectly good mood and is actually a really fun person. His more typical tantrums are five minute fits over something as simple as not being able to close the ski boots because something was jammed, or spilling a glass of water. I'm not really sure whether this is bipolar, multiple personality, or something else. My father is very nasty during these fits usually with words and sometimes he breaks things, but he never hits us. The thing that confuses me is that large things such as the death of my brother never anger him, it is the little things. I'm just trying to understand his issue so that I can read up on it and figure out what type of actions typically work best to prevent these tantrums. During a heart-to-heart he told me that if he got his issues diagnosed that our something-or-other would go up and we would have to pay more money. I feel that medications/therapists wouldn't be an option, seeing as we don't have much money. I'm here to understand his actions and to prevent these outbursts around my friends in particular, it's very embarrassing. He also once admitted to usage of a few illegal drugs as a teenager. He is now clean, but has a slight alcohol abuse that comes out when he gets drunk once every two to three weeks.