He's using the yoga as an excuse to him drinking.
Hmm, compare yoga and drinking.... yep... doesn't make any sense.
With an addict, it never does make any sense. Keep taking care of yourself in yoga class and you don't have to explain to him how you get it done. He's doing this "woe is me" game that usually gets us sucked back in. Don't feel guilty or let him pursuade you into feeling guilty because you are taking care of yourself. Do you.
I wouldn't respond. As I read his email/letter it appears that he isn't asking for a response. He's pushing buttons.