What do I do now that my 17 year old moved out cuz I wouldn't let him smoke pot?

He just started doing it in November. I found residue and calmly confronted him, he admitted and I told him it was not okay to do that in my house. He used my words as a loophole ticket to do it anywhere but physically in my house. I confied it twice after he tried to sneak back in from the woods on our property. He informed me it was his chosen lifestyle and I should respect his decision as he has only 5 months before he's 18. That I need to allow him to blossom into his own person. I told him as long as he lives and eats in a home I provide, he will have to respect my wishes. I don't see pot as evil, but I have the right to say it's not a lifestyle I chose to be around. The only punishment I gave him for all this, was he no longer gets rides to where ever he wants and a stern warning that his behavior was going to end up biting him in the , that he was going to get caught and I would not bail him out. Well, a week ago, I got a call from the school. He was expelled for smoking pot in the bathroom, having a pill bottle full of weed and 2 pocket knives. I expected he would be arrested, but there have been budget cuts in our area, so there was no Sheriff even available during school hours. He drew a line in the sand and challenged me by being so blatant. So because I love him, I responded. I told him no privilages of any kind for 10 days, after that, I would return all privilages except he could not see his friends for 10 more days, after that he could go back to hanging out with his buddies, but would have to consent to random drug testing, if he tested positive, I would repeat the previous restriction process. Long story short, he refused to comply, spent 3 days straight saying the most venemous cruel things to me such as he hopes I die of a heart attack, hopes God has relations with my backside( his exact words would be too graphic), called me the "C" word and prayed to Satan to help him. Kept arguing loudly, screaming the "F" word through the house, punching holes in the walls and frightening our 4 younger kids. All this from a young man who voluntarily attended church, never cussed at me even once since he was 2 years old. Never before said he hated me, knew I was adamantly against drug use, as his father died of a meth overdose when he was 3 ( I have never used), and I had kept my kids seperate from the rest of our family because all of them have substance abuse problems. So 3 nights ago, I let him go. He was invited to go live with his buddy and his parents and grandparents. They all live in a nice big beautiful home, have successful lives, and grow and smoke pot every day, as it is their "chosen lifestyle" I feel devastated. Like my little boy has been stolen from me. Not only by these people, but drugs, just as I have been robbed of other relationships. I know he's not my little boy anymore, I know he said all those things to hurt me..but some words punch a hole through your heart. He could have done all those things and moved out without saying he hoped I would die and calling me the "C" word... I feel heartsick at losing my son, yet relieved he is not here emotionally abusing us and continuing to turn our world upsidedown. What do I do now? Will I ever have a good relationship with him again? Will he ever truly be sorry for the cruel things he said? I have never, not even once, cussed at him or said I hated him or wished bad things upon him. Why would he be that extemely cruel when he came from a home where no on ever talked that way? I don't know what else to ask or say. Has anyone ever been through this or been in his shoes? Please tell me . Thank you