You can take a few steps to help him if he is willing to accept that kind of help.

First, cruise over to /r/personalfinance for great material on starting a budget with the YNAB (you need a budget) application or just in your own way. A lot of people benefit from building a budget because it helps keep their ongoing spending under control. If you just spend as you need to, that can get to be a problem when bigger needs aren't funded due to smaller needs getting the attention first. Prioritizing may be a 'thing' for awhile until he gets stable.

Second, collect all the information necessary for student AID, file the FASFA if he hasn't already, and start applying for social services. Everything from SNAP to medicaid should be considered. If it is available, file the paperwork if he meets the edibility requirements. The worst they can say is: no.

Third:

One time, he was out at a restaurant when he wasn't supposed to be and his father beat him and locked him in a dark bathroom for the night. He was 18 years old. His family has always been extremely rude and neglectful to him. He has suffered abuse from his father many times. He has burn marks on his arms from an iron that his father threw at him when he was younger. He has seven younger siblings (he is the oldest), who are all treated much better than him. Despite all this, he loves his family because of the few times they are nice to him.

He needs to get evidence of this happening recently and go to the police. These people are violent, dangerous, and pose a real threat. If he is living in the United States, just putting a hand on him and pulling him much less any kind of strike would be assault. Locking him in some place against his will is kidnapping and imprisonment. They are looking at serious jail time for this stuff.. if he has proof.

Finally, consider three the most important one on the list. If they are willing to engage him, the ultimate final act of revenge would be recording their yelling, any hits he takes, and all the rest when they don't "forgive" him and walking straight into a police station with audio/video proof of it.

Please send these people to jail. If they are willing to lock someone away after beating them, they need to know what it is like to be locked in with someone who wants to play hide the sausage.