How does he know he smokes? It would be wise for you to keep that under wraps. Secondly, I would think about whether or not his smoking is something that you can truly accept in your life or not before it begins to cause problems in your relationship. Next, I doubt that he would get Full custody anyway, but you may want to do some research about that or contact a lawyer. I would say that your ex sounds like a coward and he's probably just trying to scare you and intimidate you because he's jealous, but don't feed into it. Live your life as you please and ignore his negative comments. And if you have not already, go file for child support.