"poop for brains" haha, that made me laugh. Although, actually, when the people around my lfs don't know something, at least they say that and don't pretend they do. And, I can't really blame someone for openning a box full of bettas and going through to separate male and female by tail appearance only.
Get Midnight his own tank, even if you have to keep him in a koolaid pitcher for a few days first. He'll be happier, and so will your females. All of mine recovered very well from living in a community with a male, even those who almost lost their tails.
Wow, I never had somebody have a problem that was the EXACT same thing that happened to me! Weird.
Keep the girls in clean water. Watch for fungus, it looks for opportunistic ways to get at the fish, and injuries are the best...white fuzzy stuff is a very bad thing.