All you beat him up guys...guess what? That's assault and battery, if there's any weapon involved, even a shoe, it can escalate to assault with a deadly weapon. Step mom's already taking her son's side. Wanna bet she drops a dime on the OP if he touches her little darling? Guess who gets arrested in this scenario.

To the OP. You were in the Marines. They should have made more of a man out of you. Time to get your own place, even if you need to buddy up with a roommate.

 

Legally:

Get the camera video him doing it and call the authorities.

Realistic:

Beat the ever living shit out of him.

Twice.

 

ur a marine, he is a civilian... ur above beating his ass, that would be too unfair. just buy a safe and some locks. the stolen merch is a sunk cost, so let it go. u dont want to be livign under the same roof with all that tension. ur best bet is talk to him and keep ur valuables safe.