skin issues: calcium deficit? vitamins?

My free range dragon, Mr R, has had mild skin issues since he came to us a while ago. He is about 4 years old but has been with us a lot less than than, about a year and a half. He has alway had retained shed problems. Last winter, he went through a full shed after rubbing him coconut oil everyday for three or four days. Then I noticed that the skin folds on his ankle and behind the knee were kind of raw looking and I applied ointment on it every few days for the rest of the winter. It got better. Then spring sprung and Mr. R decided that free ranging in our garden was not enough for a handsome devil like himself and went off for a month. We looked up and down, left and right and could not find him. When we were almost sure he had either died somehow or been found by someone who kept him despite our many notices everywhere (we like in the countryside but there are some nieghbours and whatsapp groups, etc), he turned up in his usual spot. But he wasn't looking good. He was skinny as if he had not eaten at all, one eye was swollen shut and his skin looks as if he had shed not just the old scales, but also the new ones underneath, in some spots, mostly the low belly and hind legs.
Now, he stays out a lot as I've said, and he doesn't have a tank. He eats fresh, organic greens and beasties, but I had not given him any calcium because both his previous owner and the vet told me it wasn't necessary for adults. And then, maybe three weeks ago, one day I noticed his beard was black. It was bedtime so I put him in bed, but I was worried. The next day, the beard was still black, and he couldn't walk. I put him in his usual place, but he didn't go to the grapevine. He stayed put. I offered him food, he didn't even try to eat. I remembered the baby food always recommended here for emergencies, and fed him some (I always have one handy since I read about it, you never know and I live far from shops). He had some, but he was very lethargic and would not move. I put him in the pool, he drank and pooed, and he seemd to move better in the water, so I let him stay there until he seemed ready to go out. MEanwhile, I was reading furiously through this whole site. And I realised calcium was maybe the answer. So the next day and for two more days, I fed him baby food with calcium (which I had already, for the little ones). He was eating more and more, and on the second day he walked again! (thanks everyone!!). Since then, he looks more or less fine, apart from the skin, and he has all his beasties dusted with calcium. But his hind legs seem sore and he doesn't move them very well. He walks and climbs, but the legs are shaky and if you touch them, he squirms, as if they were sore. As I said at the beginning, this is where the skin looks worst. My question, at the end of this mega long story, is: can all of this be calcium related? or can it be something else? pictures soon.

By the way, bis eye has improved a lot, it's not swollen anymore but it seems to have a sort of whitish film on it that sometimes goes away when I put eye drops. But the orange iris is not quite visible.

It's possible he isn't getting a balanced diet with enough nutrients (calcium could be part of it). Have you tried supplementing his garden food with things like collard/turnip/mustard greens and squash and green beans etc? Since he's getting so much direct natural sunlight, he should be getting enough UVB. As for the skin issues, I'm not sure. Maybe he isn't getting enough hydration? If you see spots that are not shedding well I'd try putting some plain aloe over it to help moisturize a bit and see how that goes.