B.S.
If he has never met his brother, not going to his graduation probably won't mean much to him. As far as the tough love goes- I would not subsidize him at all. When he gets kicked out of the friend's house, let him know he is welcome to come to Sunday dinner or dinner once a week or something and that is IT. Lol, if he shows up and is polite and helpful, maybe let him run a load of laundry so he has some clean clothes, but NO money and NO place to stay unless he gets a job and shows some responsibility.
It sounds like so far he has shown a talent for getting people to help him out, but he will run out of 'friends' sooner or later and need to get serious. I don't think you are being too tough at all!