Yes, $18k national average for a single adult should be low enough for a plan subsidy. I assume he is in a higher income state due to the rent cost.
Healthcare system meaning “St Jude” or “OSF” or “Kaiser.” These Are medium-to-large organizations in the US that many doctors and hospitals fit into to provide service. These orgs are large enough to provide charity if you do a little paperwork.
Why would you assume he had any association with a healthcare system like that? He's said he had no insurance.
That said, I agree that it would be good to check with any nearby large hospital to ask about their charity programs. Better yet, just show up at the ER of a large hospital and tell them the symptoms he's got. Given the urgency of the situation, I think they'd be obligated to treat, regardless of ability to pay. Then, once you're in the system, check on their charity programs.
I assumed that because most people interact with these systems if they have a doctor or go to the ER. That's not precluded by avoiding elective/preventative care.
