mleigh, That was also my biggest fear, sharing custody with a woman who hasn't acted like a wife or mother for a long time. If her patterns remain the same as the last few YEARS she will (and is!) be leaving my D14 alone after school so she can "work late' almost every night. I know from experience that the time from after school to a parent gets home is the WORST time at my D's age. That is when there is trouble! It is when they have "friends" over at their place because mom won't be home. Kids at that age are so full of "peer pressure" and with my D going from private school all her life (102 kids in K-8, she had the same 8 kids in her class from K! They were like brothers and sisters) to a school where just the Sr class has more than 400 AND my D knows NO ONE, is scary to me!
For now my D14 spends 7 days with her mom and next 7 with me. She never really gets to unpack and has little stability. Because of my W's "need" to "be on her own" my D14 has lost her sister (D19) because she refuses to live with her mom and I can't afford to get her a car (her mom can but won't), lost every friend she ever had because her mom moved 30 miles away, is in a school that is scary to her and she hates, has lost the only home she has ever known for 1/2 the time and has had to watch her own mother act like a child. But my W insists that not only won't any of this hurt our D14 but that because my W will be "happy" at last because she is getting away from her husband of 21 years who she admits was a great husband and father, that she will be a "better mother" and that will make up for all the bad! Crazy yes, but there is NOTHING I can do to stop her and I need to direct my attention to doing everything I can to give my d14 all the things her mother won't.
I know it's scary. I know you want to protect your kids from the crazy MLC spouse but in reality, in today's society, there is NOTHING you can do to stop a S who wants out of a M. They don't need a reason any more, even if you don't want the D, all they have to do is tell the court they want out of the M and it's granted. I never thought I would need to even think about D. I had no idea that it was so easy for just one person to end a M but it is what it is.
Depending on their age, most states take which parent the child wants to live with into consideration (after a certain age in my state it's 12). That may help if you know your child will say you. (my D refuses to say she wants to live with me because she doesn't want to hurt her mom and I understand that!).
In the 8 days that my D14 has been at her mom's while in school, I have had to pick her up to take her so she wouldn't have to walk 25 min.'s because her mom has decided that being at work a 1/2 hour earlier is more important than what is best for her D14 5 times. I have picked her up after school several times in very hot or bad weather so she didn't have to walk 25 min home with a full book bag! I do this for my D14, not for her mother. Yes, it hurts knowing my d will have problems that I won't be there to help her with. Know she is safe, being taken care of but the reality is I can still do much so she knows I'm there for her. I may not be there physically but if she needs me she KNOWS I will be there ASAP. She knows this because I am now and always will be.
In the end there is a point where you have to decide that your S will be OK even if he must spend part of his time with your H. That just being there in the same home isn't the only way to help him. That while you would rather he be with you 24/7 at some point you may not have a choice in the matter anyway. What is best for him...seeing his mother in so much pain, being a "doormat" (your word), teaching him that is how men treat their wives or is it better to show him you are strong enough to stand on your own two feet? That the way your H is treating his mother is WRONG, causes pain to the person his father is supposed to love and care for. Who he SWORE he would stay with through "better or worse"?
Only you can decide when things are so bad that it's worse for your son to see the way your H is treating you and the M or if staying is still best. It's not an easy call. It s@cks to have to make it but again, it isn't your choice or fault. Your H is the one who for whatever reason has put you in this position, remember that. It's up to you to decide when and if the choice to end the M is better or worse for everyone involved, including you! Even then, at some point you may not have the choice if your H decides to end things himself.