No idea about drugs but he is a great actor. He did play a drug addict boxing trainer for a movie about boxer Mickey Ward.
It was a great movie. His performance as the brother was insanely great.
I’ve enjoyed most of his performances (never saw the Cheney movie). Why can’t these folks just shut up and act?! Sadly, thrusting a microphone in front of someone automatically makes them (and their listeners) assume they have something cogent to say.
I too think he is a great actor. A lot of great artists & performers are a-holes in person, or have some other gaping character flaw (think Robin Williams). It’s just the nature of the beast. Ironically, its probably their flaws that help make them great.