If he dies, I doubt the hospital can collect on the tab.
He won’t have to worry about the debt since death voids all debts - $500,000 is nothing when one is on death row.
The hospital may still try to collect om monies owed post mortem. They will either try getting it from his estate and possible trust fund, since his mom is known as ‘a British Aristocrat” as though that were a job description. or the hospitals may go directly to the parents, who are likely to be property owners of some means.
Maybe it’s a state law, but in my neck of the woods, debts are still owed after death. The hospital will try to collect from the estate.
When my uncle died, I administered his “estate” even though technically, there was no estate. Uncle didn’t have a will and his assets weren’t enough to formally apply for letters of administration. I still paid the bills. The only one I didn’t pay was from the ambulance service — which came in more than a year since my uncle’s affairs were settled.