I will let you know I am a 27yo male and I have been married almost 3 years and with my wife almost 7 years total.
Before I met me wife I had a 'collection' of porn and went to the strip clubs atleast once a month, when I met me wife I could tell (and oh she let me know :)) that she did not approve of it and I think it makes her feel undesirable so I tossed the porn and quit going to the clubs out of respect for her because I love her dearly and would never want her to feel that way.
You must also remember that men are different than women and some guys really just need it, if it was a big deal for me to give it up I may have started a fight over it wtih my wife but then again then we may not be togeather now, but I can tell you that some men need it just because they have a higher sex drive and some do it because they get bored with the partner they have and if anything it can spice up things and give him some ideas if anything if you are a female who is ok with it, of all the girls I have been with 80% seem to be ok/like it but 20% don't so it really is all dependant on the female.
He should still quit doing it if you dont like it but I will be the first to fess it is something that some guys just can't stop.
As far as looking at other people well in that case he is just an ahole and lacks respect for you, even if he is doing it he seems to be doing it so that you have no problem noticing and I really feel for you, I know how that would make me feel and it is not good at all.
Usually with these type of 'lookers' most of them will want to keep browing the eye candy but will get very angry if you did the same so have you tried going that route yet? I know it would not make you feel good probably but if it gets him angry enough and make him realize how you feel then maybe it will change his mind.
Too bad you have a kid with him as then we could all just suggest leaving his ass but its really had with having a child with someone as it cuts down your options.