When I had a pony come down with Laminitis he came in the the stable for a fortnight before he was even shown a blade of grass again. Only when he is absolutely sound should he be asked to start moving again.
Then extremely limited grass, and as saddlebag said, the night grass is weaker than day grass, and so if you can put him out at night and in at day that is indeed the best.
I would be inclined to stay off any kind of painkilling supplement that is got prescribed by the vet. Partly because you don't know how it's going to effect his metabolism, partly because you need to know whether he is in pain or not.
Good luck with him. Follow the vet's advice to the letter, and phone him up to ask for more if you are unsure.