I am sorry, but there is no easy way out of this one..... (from your side of the fence) to be happy as you want to be would mean that you do not get to see your son every day and to be with your son every day seems to make you unhappy for you have to see your now present wife every day.
YOU are the only one that can decide what is best here.... we cannot make that decision for you.

I think the first place to start to is to be honest with your self and admit what went wrong in the first place with a once love filled relationship.... for one does not reach the point you and your wife are at in a marriage without some time passing with things unfixed.

LoVe,
Rhapsody - ((( hugs )))