Firstly, a big hug. I lost my Mom to cancer, too and at 18 months out, you are still deep in the grieving process. It's a huge, huge loss and I hope you're being kind to yourself.
Now this:
"he finally called to tell me he indeed needs a biopsy of his thyroid but hasn't scheduled it."
Ok. A doctor wants a biopsy. That's not a cancer diagnosis. That's a "let's see what's up here." You know what's up - he's an alcoholic. He's poisoning himself every time he takes a drink.
But - HE HASN"T SCHEDULED IT. He is looking for you to pony up with concern, care and attention that he isn't matching with self-care. He's happy to call everyone you know and use the c-word - and he knows what a huge trigger that must be for you and your family right now...
But he won't make an appointment, get some answers and take responsibility for himself.
You have every right to do what he can't or won't do - which is care for yourself.
And you don't need permission from -anyone- to do it. It's your god given right hand your number one responsibility.
SL x