Does the rest of the family comment to you about DH's grumpiness or to him? If they only remark on it to you, tell them to talk to him about it. He just might be more willing to listen to them than to his wife! Men often are.
Obviously, you want and feel you need to help your son, but I think I can see a little of what is bothering your Dh, too. He probably had got used to being alone with you, and doesn't want that to change.
Point out he is being unreasonable being furious about your DS having given up his accommodation. You say it was a live-in job, and as he has quitted his job, he would need to move out, wouldn't he?
Ask your DH what his ideas are for a solution - being furious and grumpy is not a solution.