One of my rules that I had from the get go with my FI is that don't ever lie to me. And he hasn't, he's a smoker. But he smoked since he was 19, he did try quitting (which I didn't tell him to do, he just did it) and he struggled with it. About 4 months after quitting he started a new job, pretty stressful and within a few weeks he started smoking again just one here or there. Now 2 years later he's back to his regular smoking but he won't smoke in our new house. He never lied to me, he told me he was struggling with it and really stressed which is why he reverted back to it. Plus he got sick from the Chantix and and had some crazy nightmares from it. However, he's told me in the past that when we have kids he's prolly going to try quitting again and hope that it stays.
The other issue regarding the women's boobs. Identify the source of the pictures before you do anything. My FI gets forwards from the guys regarding stuff like that and for the longest time he was saving the images then forwarding (didn't know he could do it right from the msg). Not that big of a deal to me either way. As long as he's not getting them from another women or stepping out on me. That's another rule...cheat and SEE YA!...been there, done that.
Long story short sit down have a conversation. Communicating is key to the relationship. Level with him, tell him the reasons why you don't like what he's doing.
Good luck and keep those communication lines open!