Cut ties with your ex-husband. His offer of a “free stay” is rather insensitive. He exploited your mother’s trust and is now profiting from your family home.
It’s best to block him, sever any contact, and interact solely through attorneys if necessary. Engaging with him will only reopen old wounds. Regarding the medical bills…
You may want to hold off on payments until you consult with a lawyer.
Depending on your jurisdiction, you might not be legally liable for those bills, especially if the estate—currently under your ex’s control—should cover them. A legal expert can help you navigate this matter so you avoid paying more than necessary. You were there for your mother every step of the way.
You deserve a significant portion of her estate. It’s your right to contest the will. However, it’s worth noting that some parents opt not to leave any of their wealth to their children for various reasons, like the cases of parents who felt their son deserved all the money over their daughter.