Hi Space,
You say that when you ask for help he can be so passive aggressive, bad tempered or unpleasant - does he know he's coming across like this? Mine wouldn't, it's just that he'd be so concentrated on the job in hand that he might act in a way that, to me (and others), it appears as though he's in a really bad mood, but, actually, he's totally fine, he just doesn't have the 'energy' to be able to act like that. It takes a lot of guts for me to turn round to him and ask him if he's in a mood, or, alternatively, tell him to get a grip and sort his attitude out, but that is all that it takes. (Unless he is in a mood, of course!). Are you able to ask him about it after an incident like this?
Had never thought of the putting off of jobs as being related to it all, but it could be. Our front door was broken for a good couple of years before he fixed it! If anyone else asks him to do something he's there in a flash, but something at home? I can forget it! Amusingly, I asked for his help cleaning the kitchen cupboards about a year ago. He agreed, cleaned one off his own bat then asked, in all sincerity, if that was it done (why that one cupboard was different to the other 12 I don't know!). He mentioned, the other day, that we need to clean them this week. Don't know if he'll get round to it or not. I'll probably do them myself, but it would be so much easier if we could do them together.