Gracy, I am unclear why you connected his fantasizing about the coworker with his use of porn. Men have fantasized about the women that they are in close contact with for a very long time, and online porn has been available since mid-90s. The drinking/smoking part, too - how is that connected? Your first paragraph describes the interactions between your H and that woman, at work. Based on what you wrote, your H was sober throughout those interactions and contact.

From what you have described, it appears that he is now playing the role of a mischievous kid who was found out and who is trying to be good or to pretend to be good. And you are playing the role of a big enforcer of discipline in the family - no smoking, no drinking, no porn, no touching female coworkers, curfew at 9PM.

This is not going to work in the long term. For a sprint, sure; for a marathon, no way.

Could you select ONE thing that you want him to stop doing for now? What would the most important thing be for you? Pick your battles.

Compromise - e.g. maybe he can go outside to smoke if you, understandably, do not want second hand smoke in the house, neither for yourself nor the baby. Drinking - how about he drinks at dinnertime with you present?

You also wrote that you did not know why he did that TO YOU referring to his fantasizing about the coworker. When you fantasize, do you fantasize just because thoughts, feelings, and fantasies cross your mind, or intentionally, as a way to do something bad TO SOMEONE?

I think the main problem in your r/s is that you took the role of an authority figure and he took the role of a boy who is trying to hide his misdeeds.