Asking for a divorce due to fear of doing wrong

Since I got married and I became Muslim, I don’t drink or smoke. My husband smokes tobacco and weed, which he thinks he will not refuse to do in any case, because in his opinion smoking weed helps him to relax and it is not unhealthy.
I am afraid that one day I will start to think that the way he is acting is good, and I might start to act in same way. I prayed Istikhara prayer many times, but still confused what to do is the best.Am I allowed to ask for a divorce in my case?