Hi realperson
There could be many reasons why he is irritable and snappy, some related to alcohol and some not. I think first he should probably be checked out by a doctor. I find it interesting he is blowing up about watermelon because diabetes can cause mood swings like that. Has he had his sugar and/or blood pressure checked lately?
Perhaps you suspect he has relapsed? If so, I always advise folks to trust their instincts. Do what you need to do to take care of you FIRST. (((hugs)))