Welcome, but sorry to hear of your boy's issues.
I second all of Desert's advice, except for getting him tested right now for IR & such. Can be necessary, but the tests also have their own issues, including potential for further laminitic 'attacks'. So of course, look into it, ask your vet etc, but I'd avoid it at least until he's better, just assume he's IR & treat him as such. If he's 'foundered' because of being long term overweight, it's likely he is. I'd be inclined to soak/drain the hay if it's 'improved' pasture hay. Also check out barehoofcare.com
Hoof & horse pics, see link in signature, xrays if poss, and more info if you would like specific hoof advice. In addition to the Chromium, there are other mineral imbalances which will affect his metabolism & hooves. Namely magnesium, which is REALLY worth learning about. Mg Chlor is a good, bioavailable source. And don't quote me on it, but I think it's Mg deficiency(or too high Ca(?)) that has been found to make horses more sensitive to the sun too.
Of course every case is different, but your horse 'should' be well over his laminitic attack by now. So either the metabolic/systemic problems are still ongoing, &/or there are serious mechanical issues with his hooves. Yes, exercise & free movement is indeed important, but so is comfort. So if your horse doesn't want to move, ground's too hard without padded boots or such, I wouldn't try to force the issue. Bute may of course be necessary, but it also can cause further issues, esp if long term. I'd be getting him off it ASAP & give probiotics as well, to help his gut heal. There are also effective herbal alternatives for pain, if he's too severe still.