Love with an addict

My relationship has been a very rocky one to say the least. I have been with this guy for years and when i first mett him i was 15 1/2 n he was 16 1/2 i was a resposible kid got good grades loved to learn new things at school and impress my teachers with my intellect. He was the bad boy did drugs partied hard and didnt give a f##k about anyone because he grew up in a home where he had to care about getting by and getting high thats it. I mett him and he acted like he wanted to change and better himself. He was ashamed of the drugs he did. For 2 years he did methadone and heroin at the end and i cared to much to give up on him. He was arrested and sentanced to a year. When he got out he swore he would stay clean. that didnt last long and i could not handle it anymore. We broke up for 5 months and then he messaged me saying he was doing better and wanted to meet with me. I went for it.

Now he has been clean from the big drugs for a long time occasionally smoked weed and lied to me but was caught and continued to lie.
He is trying to convince me it is ok to smoke weed every so often and it will help his MANY psycological problems.
I do not condone any drug use due to our past

he sais if i do not allow him to smoke weed i do not love him unconditionally.

I told him he can smoke weed and i will always love him but i can not support the behavior and would have to remove myself from the situation.

I believe he is chasing the high.

not to mention i have a full time job pay the rent and take us out to dinner when he uses up his food stamp card (buys monster n candy not real food)

I dont believe anything will teach him how wrong he is... any suggestions