Maybe someone should start a thread on dealing with an affair.
I do not think we should lose sight of the fact that for someone to have an affair is an ugly hurtful and emotionally abusive thing to do, and for anyone normal it is a huge thing to get past. We need a lot of tenderness and help in this.
Yes, pride comes into it, and yes the desire to punish comes into it as well, but if we set aside these two responses/reactions, an affair is never the solution to either personal or relationship problems. It is never the fault of the person who is left. That is the abuser's perspective and sometimes we internalise this. An affair is a wholly inappropriate response to problems and an indicator of someone who is hugely emotionally immature.
We hurt when we are abused, and part of that is a very normal and healthy response: we need to be very careful how we deal with the abuse and the abuser. If you are in ay doubt about this please do read Frank Pittman's article on affairs. [available on the internet]
One of the things that disturbs me slightly about some recent posters on the boards is that this is not the first affair in the marriage. A serial adulterer is almost impossible to deal with - they have trampled a major boundary, 'repaired' the relationship and are stupid enough to do it again.
Let us not lose sight of the fact that actions have consequences: we can choose to forgive, but there is also cheap grace. If we value ourselves do we want a marriage/relationship at any cost, and price?? These are hard questions. I sense that you are torn between self respect [not the same thing as pride] and love, which is a hard place to be. You also need sympathy, not just a 2 x 4. You are dealing with the fall out from your husband's emotional stupidity, buttressed by his mother's support [which is not inevitable, and not helping anyone, she should just butt out imo. Validating bad behaviour is not the way to help people grow up]
I respect the advice you have been given, but I am not sure I agree with all of it. I do not think that a man who abandons his wife and child does have his child's best interest at heart, and I think you are correct to question this - not his love, but his commitment. As his mother you are the primary care giver. Many men who leave their families lose interest in their children [not all, but the stats are frightening. And it is not all about the mother being 'difficult'].
The question might equally be asked, is you husband asking for 50% custody to punish you? The child's best interests are paramount.
I hope this does not come across as unasked for advice. I always assume that when people post they are asking for input. My advice could be wrong!!
Sometimes 'rightness' is not about being right but being wise. Love is important, but tough love matters too, as anyone who has raised kids knows.
