Hello, ArtMachine
I have an adult son, with whom establishing boundaries has helped me to live a healthier life; it took time to get to this point. Much of what I learned about boundaries, along with a lot of input and support, came from forums here at SR.
Like you, I had questioned what I should do, sat with the guilt and anxiety but also welcomed the peace and sense of hope, once detachment began.
Your decisions are yours. I won't advise. Just know that we parents and others here at SR, who've walked a similar path, understand, support and encourage you.
As far as healthcare bills - when he was a minor and even a few years into adulthood, our insurance as well as paying out of pocket took care of son's medical, MH and D&A treatment costs. However, once he was no longer insured on our policy, was not living in our home, and a couple of bills for ER services he received were mailed to my home -- I chose to return to sender, noting he is an adult and no longer lived at this address. It worked out. He handled it.
Hugs. Hang in there.