For underworks tanks, stepping in and pulling it up by the straps is pretty effective. I've also had success making sure the fabric is pretty flat as I pull it on over my head, which lets me grab ahold of the bottom edge between my shoulderblades and work it down. Getting it off, I pull it up from the back, or from the straps, then get my arms inside, bend over, and kind of push the straps up until the bulk of it is free. It's pretty tough going; I've pulled muscles. The binder itself is fine, though, and I've yanked on it hard enough to shred any other article of clothing I own. Those things are indestructible and can, with sufficient force, stretch to way over twice their resting size.
As far as the mental health stuff goes, and I'm sorry you're in such a bad place. I've got no platitudes, just sympathy. I hope you find a reason to stick around. And, if you do decide you want to talk about it here, we might be able to come up with something useful-- a lot of people have been through similar stuff.