I think living difficult in laws and an unsupportive partner can be a real recipe for disaster.
Im reading that they have behaved badly towards you and your husband would prefer if you just move on and not rock the boat.
He is putting his needs ahead of supporting you and making it clear to his family that his wife and children come first?
This often happens with men put in this position.
They don't like conflict.
They have an unhealthy dependence on their family.
They are quite selfish.
They certainly aren't loyal.
I think loyalty is critical to a good relationship.
Have you spoken to your husband and made it crystal clear that his behaviour is not acceptable?
Have you told him you are NOT moving on from this without a satisfactory resolution?
Have you told him this could be a deal breaker for you?
Speaking really plainly is crucial.
He needs to know exactly where you are and how you feel.
Is there a middle ground that ye both would be happy to occupy?
Is there room for compromise?
How serious is his family's transgression?
If he makes it clear he is never going to have your back and put you first, I could well imagine that it ould end a marriage.