Wait, you're a gay dude? Ok damn this just got even weirder. Disregard that lol.
Whether you were aware of it or not, you were nudging him down the path he's on right now. He's going to be in an early grave if he continues, even if it may take years.
Imagine what it would do to you mentally if he dies of a heart attack a few years down the line? Knowing you were partially responsible?
So act now, do everything you can to reverse his course, including leaving him if necessary. God, what a fucked up situation.