Welcome, Plaxmax.
This young man definitely seems to be out of control, regardless of the reason.
Sadly, nobody can make him change unless he decides himself to do it and takes actions to back his intentions. All the love in the world will not save him, if it would not one of us would be here.
Allowing someone like that to live in our homes is giving ourselves a front row seat to the drama and it rarely has a happy ending. The hardest thing I ever did was to make my son leave but it was also the best thing I ever did, for him and for us.
What helped me, what literally saved my life, was to go to meetings, get a sponsor and learn how to work the 12 Steps and apply them daily to my life. His family could gain a lot from this but like the addict, they may not think they need this and simply not go until they reach a point of surrender.
Maybe you and your girlfriend could try some meetings and see if they don't help you regain your balance.
And stick around here, others will be along to welcome you. We truly understand that dark place where you stand right now and we hope that sharing our own experience, strength and hope will help you in some small way.
Hugs