Mom died 1 year ago. Dad still paying medical debts

My mom was diagnosed with stage 4 liver cancer in 2023 and fought it for almost 18 months. She passed away last February. My dad has heart problems and has been in and out of the hospital.

He revealed to me last night that he has approx $300-400k in medical debt from mom’s chemo that he’s been paying $160 per month on for the past year. He says it’s 0 interest and he has no expectations of ever paying it off in his lifetime.

The question I have is: he is working on end of life planning and the inheritance for my sister and I. My parents were always fairly well-off and didn’t worry about money but after watching him for a year, I can tell that was all my mothers influence. He has blown through a huge chunk of their retirement in the last year. He has a home that should net $800k- 1M but I doubt he will have any liquid assets left to pass down to us. This medical debt would take an unexpected large chunk of the house proceeds, if we would have to pay it.

I have been a long time reader here. I think I understand that the estate pays the debts before any inheritance is passed down? Is that correct? Is dad responsible for mom’s medical debts? Or should he stop paying them? Would that balance have to be paid out of the proceeds of the house before we could collect anything? I’m trying to advise him but wanted to have more facts before I did.

Thanks in advance.