Are you sure the cough is from the pot? I'm kinda ignorant on that one, but I have a nasty cough, and have never smoked anything a day in my life. Maybe he should get it checked out, just to be sure? Just a thought...
Either way, I am so glad you're putting yourself first here. You should never ever feel guilty for doing things that you want to do, just because he doesn't approve. He does things you don't like... so why should you try to please him?
IMHO, him saying that he is contemplating quitting, but loves it, is just a softer way of saying he's addicted and the pot is not going anywhere. But I'm sure you already knew that
You're in my thoughts tonight.