God I don't even have the words to express the pain and anger I feel for your son right now. His sister is right, leave him alone. You very very clearly showed him how little you trust and care for him. You did everything wrong:
You didn't stop for a second d to think if your son was capable of doing this
You didn't stop to think if there were any external influences (ie stepdaughter father, there is no way this is the first time he's caused trouble)
YOU DIDNT LISTEN TO YOUR SON'S POIMT OF VIEW. This is he part where you failed as a father. If he had done it, I'm not saying you should have taken his side, but he didn't. I you didn't give him the chance to explain himself.
You chose the most cruel and horrible way to punish him for SOMETHING HE DIDNT DO.
You kicked out a child. That's illegal.
You never thought to reach out to him in the last five years. Seriously, did you never care to check up with him?
Leave him alone. He deserved better than you. You failed him. He made his way on his own when you turned against him and chose your new family over him.