I always had issues with my in-laws, mainly dealing with lack of boundaries on their part. My husband was never able to make a break from his family. In many ways, he put his family's needs above the needs of his wife and children. I had access to his email and Verizon accounts so I read so many hurtful messages and emails between his mother and him. She was actually the person that got him the attorney and really guided him with regard to trying to remove my parental rights. Now he wants to come home and wants me to accept a new life where he and I are a family, but he is allowed to bring the kids to family parties and to his parents house without me.
There is no way that I can give any meaningful advice without knowing all of the countless complexities of your situation. I CAN however speak to what has been quoted above.
No matter what the reasons, how good or bad they are, he probably feels justified in the above. I don't care if he is even 100% right and you are 100% wrong. Even THEN, what you stated above is not appropriate behavior on his part.
If this relationship is going to work, he is CERTAINLY going to have to follow by the following rules (and you too):
Never complain to your family members or friends about your relationship problems. Don't do it. Instead, you talk to your partner. By not following this rule, you are violating trust that is paramount. You are disrespecting your significant other. The only time someone else should be involved is when there has been REPEATED attempts at communication, the communication isn't working, and one is considering leaving the relationship. Even in that situation, there is a HUGE subjective area about what is appropriate and what is not.
Even BEFORE you had problems, he has created problems by not following this rule. Now he has a mess to clean up. If he wants to be with you, then think about it: at a minimum, it means he loves you, has some sympathy and understanding for whatever problems you may be having, etc. I may not like everything my significant other does. But I know we love each other. She may even do something wrong. But I can talk to her and try to understand the reasoning behind the actions. But if I complain to a parent, a friend, a co-worker, another family member, I am only giving that person one side of the story. I am robbing the other person of their privacy, dignity, and respect. Also, although perhaps unintentional, by telling someone all the bad things that frustrate me, I am essentially telling LIES about my significant other, because the listener only hears the bad things and MY frustrations without considering that there is a human being on the other side of the coin.
He may not fully realize it, but what he is doing is not being able to come to terms with the rift that HE created (even if he WAS 100% right in his complains, and I am not saying he was). He created this rift BEFORE there were problems by not respecting appropriate boundaries. Now, you have in-laws that have a very unfair view of you. You have been robbed of the right to be seen as a human being with another side to the story.
If your relationship is going to work, he is going to have to fix this. After all, he is willing to come to you and spend the rest of his life with you. He has a moral obligation to now get his parents to understand exactly what he claims to understand, and undo all the damage he has done. Sure he is upset because you did, X, Y, and Z. But, whether he fully realizes it or not, by wanting to come back, he is saying that he can be sympathetic that you did X, Y, and Z, and that you are a good loving person whom he respects, admires, and understands. He is willing to work on all of these things because he knows there were no bad intentions. His parents need to be brought up to speed. He has to get his parents to feel the way he feels. He has a difficult job, because their feelings have been one sided for far too long.
He needs to read this.