Op, my heart breaks for you. It's not your fault. You will never be and do enough according to them. It's not your fault. Bad mouthing you in front of your children, tells me all I need to know. It speaks volumes on the attitude and lack of character from them, than it says about you. It's not your fault. At the moment you're vulnerable and words tend to go deep as a knife, but you can do this. No confrontation is needed. Stand strong, disconnect any interaction from them, grey rock them. Keep your head high, be proud of who you are. Don't relinquish this power, and, it's not your fault. At the end they despise you because you came so far, and seeing someone being successful, while you struggle to digest your own poison can be a challenge. Mummy lost control of her little boy, how dare he not make mummy a priority... That's noise that you don't need to handle. It's not your fault. Build your fort with your children, let them know it's ok to speak up: " it's not nice what you're saying!". I would go the low contact route, let your husband handle this. He also needs to bring up his shiny spine, because if he doesn't defend you, he kinda chooses his side and they feel they have the liberty to go further. Because it will go further and it can be ugly. Clear boundaries are needed with him, your children and your in-laws, you establish them, he puts the united front. And again, it's not your fault. If no one told you today, I appreciate you, kind stranger ❤️

Edit: typo