I don't think you are being unreasonable at all.
If you haven't addresses directly with your in-laws, you could always do so. I don't think I would accept any explanation, but at least this way they can 'explain' any side you haven't considered or don't know (but highly doubt it)
But honestly I think the best thing to do, at least for now, is to prepare yourself for your little ones arrival and enjoy the first few months of parenthood with your husband. It is a big life change and you need as much calm in your life as possible.
Enjoying the family you have created is the most important thing, and you and your husband need to be there fully supporting each other as much as possible.
What are your husbands thoughts on no contact?
If they can treat their own sons like this, then there is no telling how they can treat their grandchild. It might hurt to not have contact for you, considering how close you seemed to have become to mother in law, but protecting your child might just mean no contact is best, and if your husband feels this too, then as difficult as it feels, go wit this.
You may find after the birth of your child, the in-laws attitudes change and they come to you. But if this happens, I would make sure you voice your feelings regarding their attitudes and let them know you won't stand for this type of behaviour again.
I wish you all the best on your journey to motherhood xx