Maybe call a meeting of those who live in the house - and already have a list of the chores ready - go around and select 1/person so someone doesn't get all the "easy" chores

Remind them that you're not the maid/mother of the crew. Prep yourself - run through it with a friend in advance so you feel confident to handle any way the conversation turns.
That's a lot to handle and I agree with other posters, he's never going to voluntarily take on any more - it's easier for him to get more and more comfortable and do even less.