What should I do, I feel that he is trying to scare me so that I allow him to smoke, drink alcohol n roam day in n day out with his friends
You can't control those things. If he chooses to drink, smoke, and roam with his friends, that is his choice. What is in your control is how you react to him doing those things. If you don't want to be around those things, then you can set boundaries and refuse to be around when he does those things.
I find that it isn't very helpful to try to figure out my partner's motives. It is too easy to get tied up in knots when thinking about things like, "He is trying to scare me." A lot of times, my husband has no idea what his motives are. More often than not, he is being impulsive and isn't really thinking about the consequences of his actions. It took me a long time to NOT take the stuff that he does as personal. He could be doing those things because they feel good and that is why he does it.
What can you do to protect yourself from those things?
What kinds of lies has he told his family to get them on his side?