Usually when you make posts like this I'm hesitant to answer, because I know you've been through this for a long time, you've tried everything, thought of everything etc. and I feel I don't have anything substantial to offer. But here goes.

I agree with all the ideas that have you working over the Internet. Stuff like building a forum, where you really have to do little else other than hosting, because you can assign mods and everything. It can be used for exchange of ideas, or more tangible things. Revenue can be generated from ads or donations, so that you don't have to charge people for using it.

It's been suggested to you before, I know, but maybe something that involves writing, like a blog. You can write at your own pace and see how it picks up. We'll advertise you everywhere!

I'm also trying to think about a service you could sell and not have you answer "but I never know if and when I can committ for something." Probably something that involves generating written content, like ads. A solution is to have a partner to pick it up when you're not up to doing it yourself.
Or - sponsor someone. You may have a friend who's, say, a lawyer. Help them open their office, get a part of the revenue. Someone who works alone and provides a service is much less risky than a restaurant and you're getting around the part of not having a degree of expertise.

I'll come back if I think of anything better. For now ♥