I actually think you'd be ok adding the loaches back in, as long as they are kuhlis, not anything bigger. However, they are very shy and in groups of less than 5 you will NEVER see them. I'd get at least ten. 6 bettas, 5 otos and ten kuhlis is not an overstocked tank, IMHO.
I would also recommend not getting the ramshorns. Seriously not worth the bother. If you want a snail, get a single nerite. Between that, the otos and the shrimp, I honestly don't think you'll have any algae problems. You'll definitely have to get the otos eating commercial food (which can be a problem) because there simply won't be enough food for them otherwise.