Not so much the previous rotation. I think he has ongoing laminitis that may or may not be causing further rotation. The previous rotation indicates that he's had it before, as do the rings in his hoof. I would guess he's IR, but your vet can do blood tests to confirm. The way you're managing him isn't necessarily bad, but it's not working for him. There could be something else going on, so you'll have to talk to your vet. I think proper trimming will also help, but the underlying issue needs to be addressed.
As far as getting him off the grass, is it not possible to put a few cattle panels together in the pasture and keep him in there? Those panels are cheap and easy to handle, and he'd be able to touch noses with his buddies. You'd have to bring him water and hand walk him, so it's more work, but really anything will be. I think the grass is not helping him right now.