Well. Rain rot is gone. Or seems to be. No more scabby bumps, and none seem to be forming back. Thank you very much, MTG.
For his weight, he's gone from a 3.75 back up to about a 4. I refuse to ride him still, want him to get enough weight back on to actually look like he could handle it. I know he could now, but hey, I waited 6 years or so to swing a leg over that back, I can wait another month or whatever until he's filled back out a bit.
I'm beginning to accept that I'll probably never cover up those ribs I always see (as he ends up with signs of being too fat every BUT his ribs (gutter back, plump belly, fatty deposits around rump, tail head, elbows, neck, etc)) but I would like to get his rump and his top line filled back out. Right now he's on a grand total of 4 cups of straight oats and 3 cups of sunflower seeds every day, with about 6 flakes of hay total, too.