RJ- Your husband sounds a bit like me with tasks and such. I used to focus on the other person's "need" to remind me. I ended up doing some extensive testing and found out that I have ADD. I take pills for it, which helps, but it is still an effort to remember those chores that need to be done (at work and at home). I got in the habit of using certain to-do lists, calendars, automatic reminders, etc., in order to constantly remind me of things that need to be remembered and accomplished. Things still fall through the cracks from time to time, but it's a huge improvement over the way things used to be.
One of the biggest improvements came in my ability to take responsibility for my own actions. It sounds like your H might need some help in that department.
As for the deck, why not get someone else lined up to complete it and maybe even start working on it. Perhaps that's the kick in the pants he'll need to do the job. It's your house, too.