OK! Update. We randomly decided to get rid of and/or rearrange some furniture downstairs - Hoddy Toddy's domain. All of the furniture we got rid of had been here since we first got him, so it's not like any of it was added recently and freaked him out and that's why he stopped running around so much. But we have these two small arm chairs that when we first got him we had side-to-side. And then at one point we decided to put them in kind of an L shape, with one of them with its back to his cage. Now, it's not like it was up against his cage at all. There was plenty of room between his cage and the chair. With this furniture re/moving, though, we arranged the chairs back to being side-to-side. Anyway, it's sort of hard to explain without drawing your guys a blueprint ... but basically, Toddy now has a clear view of the entire room from his cage. He comes out into the middle of the room and goes down the hallway so much more often now! I still think he's a bit of a lazy bum ... but this is a big difference to how he was acting just like, a week ago. I don't know if it has to do with changing the lay-out of the room, so now it interests him more, or the fact that now he can see the whole room and so perhaps feels more at ease. Either way, I'm happy he doesn't appear so depressed.
*He is an only bunny. I've been thinking of getting him a bunny friend ... I just need to convince my fiance! And I knowww I'm no substitute for another bunny, but the reason I've been stalling in getting him a friend is that I work from home, so I spend nearly all day long downstairs with him, working from my computer on the floor (you should see the rug burns on my elbows - ouch).
*I don't know why he's such a weirdo, but I've never been able to interest him in tunnels! I tried making things out of blankets, and leaving boxes around and stuff, and he just seems scared by it all.