Good questions. I am the mother of an RAD who's been clean/semi-clean for more than a year. My first thought about insurance is that you help her sign up on the Affordable Care Act -- being a single mom & a homeowner, she may very well qualify for excellent health coverage at a cost you might not be able to find.
www.healthcare.gov There is a circle/link on the right side that you can click that says: See if I Can Get Lower Costs." Perhaps suggest this to her and offer to help her sign up online, but not much more. If she does that and still cannot afford it, perhaps you pay that premium for a while.
As for the father of her child, I think it has to be her decision. She's the mother, he's the father. Unless she is in physical danger, I think it has to be her decision. She has to learn how to navigate her world and that world may indeed have a drug-addicted father of her child in it. If you believe your grandchild is in danger, it is okay to bring this up with her...ask what the plans for the visit are...
I know firsthand it's tough being the momma of an addict in recovery. My heart goes out to you. Try to focus on what you know, what you can see, and stay in the present moment. I am working on that as well, every moment of every day!