Has he been checked by his doctor since July? He may be having some depression from having to face his mortality (going through the angioplasty) or perhaps he's developed another health problem related to ischemia some place that's affecting his personality. He may not appreciate it but if you can, share with his doctor the changes you've seen in the last 4 months. There are no "nice" pills for him to take but the forgetfulness and fatigue should be checked.
My husband has a similar history - binge drinker for many years but over a period of 2-3 years this was a nightly occurence. Some years later he developed an altered personality, becoming moody and angry. The children, now grown, called him "Angry Dad" (as in "The Simpsons"). He had a stent 3 yrs ago but there has been no noticeable change in behaviour, health, anything and his memory is becoming increasingly bad. I, too, am struggling to cope and do not know how much longer I can continue to take the highs and lows, the constant changes in life and lifestyle, the nastiness and the temper. I urge him to seek further medical help but he refuses. I have asked a couple of questions on this forum, perhaps, if you look them up you may find some answers/similarities. I sympathise with you and know exactly what you are feeling. I've gone through the depression angle with him but antidepressants didn't really help and, like virtually all medication prescribed to him, except his heart medication, he couldn't be bothered to keep taking it and questioning or reminding him simply led to more anger. Sorry, not much help but just to let you know there are other people out there suffering the same.