i agree with the other posts it sounds like possible bipolar and it is very hard on familys to deal with. My son and husband are both bipolar.
It could indeed be bipolar. I guess your Dad needs to choose to go seek help. It is like walking on egg shells around someone who is mentally ill and is not on meds. Just do your best, and check out the NAMI website, that's the national alliance on mental illnes. That may help you.
Hugs
Bradian
these can be symtoms of bipolar this disorder runs in my family i am not effected by it but my sister is and she is on sever medications and often quits taking meds during manic stated that are the highs thinking she is cured he needed help from doctor to manage the high low states of his mood and if he is aggressive he may well become violent so be carefull