Soooo an update... I've asked my friend if she'd let me keep her betta and she can have one of my healthy ones and she agreed. He seems to "get better" but then declines, then gets better. I noticed, when he was swimming normal that his belly is always bloated. And since he won't recover from SBD it is definitely permanent. Again, if he didn't have such life/fight in him, or actually was sickly, depressed, and listless yeah I probably would have considered culling.... But he doesn't seem too bothered from his condition so I'll give him a chance!
So, I asked my friend also about his old owner. She said he dumped a lot of food each day!! So yeah... He's the survivor of that home, and now he's with me. I do have a question... Can I stop the Epsom? Also, would it be okay if once a month or something he'd get an Epsom bath? Idk if it'll help. I'll also see if he can be okay without Epsom anyways.