This guy sounds like a "lowlife" to me. If you feel like your mom or you are in danger, or are being abused (phsyical, mental, or emotional) then you need to put a stop to it. You should wait for a time when you can talk to your mom ALONE, make sure he isn't around. Tell her how you are worried for her safety & your own, tell her she deserves to be in a healthy relationship, not with an abuser. Tell her how much she means to you, & how afraid you are that he may do something. Also, get as many people to back you up & stand behind you as you can. Family members, friends of you & your mom's, who you can notify if something ever gets out of hand. I'm sure there are people who love your mom as much as you do & don't want to see her get hurt, or worse. (God Forbid). If you plan on reporting him to authorities or need to get a restraining order, then do it. Just make sure you have some good people in your corner, who can help you guys out if you need it. Maybe you & your mom can make arrangements to stay with other people for a few days, weeks, whatever. Good luck, & God Bless you for wanting to end your mom's pain, she sounds like she's already been through enough. She seems like she has a great son,
& I hope you guys have many many more years together.