Sounds like you are in a great deal of pain.
Take your focus off the addict-- and it's wise you are getting his stuff taken out
of your house and to him ASAP.
Some therapy for you would helpful right now to process what' going on
even for short term.
I suggest with a therapist who actually is trained in addiction and its consequences.
He may be keeping up the facade for the moment, with his Mommy's help to
pay bills, feed him, do his laundry, etc. but it will all come tumbling down
at some point.
Meth is a very harsh mistress they say, and always demands more.
He's borrowing against the future heavily by continuing to use.
Distance yourself as much as possible.
I don't think all addicts can be lumped into one "they" package and generalized about MissUs.
It does seem that addiction causes people to act in ways they never would sober,
but who can say what your ex's underlying character was before use?
It sounds like he had a problem with abuse and anger which may be entirely
separate from the drug use, but made far worse by it.
Don't worry about that now that he's out--take care of you now and let him deal with his own mess.