I know this is going to sound really, really awful...but if he gets that worked up over the fact you had a cig...and is making a big song and dance about not being able to trust you, I'd be questioning HIS trustworthiness...if you get my meaning.
It is almost like he is trying to blame you for the desolation of your relationship, when really a relationship breakdown is rarely the result of one persons actions. If it is, it is usually because that person is incredibly abusive (i.e. in the case of domestic violence both physical and mental) or the one person has severe issues. But this..having one cig after a MC, to cause that reaction. This would instantly make me suspicious of his motives.
Also the way he comes back, has sex with you, then says how he thinks it's worthless. This man is using you, he's trying to blame you entirely for the break up of your relationship and that's just not right or fair.
Lets play devils advocate here. He's vehemently opposed to smoking. For him, smoking is a deal breaker in a relationship. You two have been through a lot. He should have some respect for you and trust, especially considering you have been trying for a child together. Even if you have had that one cig; I am betting the writing has been on the wall for your relationship for a long time, and while you have dissolved into the world of TTC then unfortunately the horrendous processes of loosing a child, has masked this. But he is just as responsible for that writing. If not more so.
You need to get away from him. You need to set yourself free. You are worth so much more than this.