Glad to hear he is doing better!
I would say 2 ADF's, 1 Betta, and 1 Nerite Snail would fully stock your tank. Nerite snails are killer algae eaters, and they wouldn't be nearly as difficult to keep as oto cats.. I got 4 oto's and within a few days 2 had died; I still have 2 so hopefully they make it.