You are a very beautiful person. You are struggling with this because you have such a good heart and you cannot understand how you could be treated so badly by family. You gave your mil 8 beautiful grandchildren. You raised them while your h got to embark on his career. You deserve to be treated so much better.
I think for you it is time to deal with these issues and that is why you are struggling with them. Most of us still have to struggle to forgive our spouses so we have put the inlaws on the back burner. It is time for you to work through these emotions. Take as long as you need.
Maybe you need to grieve the loss of that relationship too so you can have a new one with your inlaws. I don't know if you will ever get closure but maybe as time goes on the pain will lessen a little.
I do think you really do think that you are being brought to this in order to heal and move on then you can have a brand new marriage. Better than ever like you deserve.
I don't know how to go about doing it really except to not deny those feelings.
Your faith brought your h back. Your faith will help here too. Just give it all to God.
I wish I had some real answers for you.
I know you will get over this next hurdle also. You have been through so much and you are such a strong woman.