Summer start is different from the regular session, but in any case it costs 8k you don’t have. So, that’s it.
Did he take AP calc and Ap Econ (micro/macro) with scores of 4 or 5?
Please don’t worry about “things that may happen”. Even if he’s at PC, you won’t “pop down” - okay, perhaps for parents’weekend, to take him out to a restaurant, but not “if there’sa problem”. He needs to figure things out by trial&error. You’ll equip him with medical basics (anti vomitive, anti diarrhea, bandaid, paracetamol, cold medicine, etc, etc) and a wikihow laminated page about laundry, and he’ll manage (more or less, then better and better), like hundreds of thousands of freshmen every year everywhere.In addition, even if he attends PC, he needs to be fully confident he’ll be able to be independent, as independent as if he were in PA.
As for his sibling’ (very serious, I understand) medical issues, he can’t drop everything to rush and be at the hospital each time his sibling is admitted- even if he feels he has to or wants to. He’ll need to focus on his studies, his work study job, attending office hours and/or meeting with tutors to refine his paper or check he is learning what he’s supposed to, plus making friends, staying healthy, networking, participating in clubs good for the former or the latter, in short grow as an independent, resourceful young adult who’s successful in college, even if he sees himself primarily as a brother. Honestly trying to rush to the hospital more than once or perhaps twice in the semester could derail college entirely for him. Classes go much faster - the entire 10 months of calc AB are covered in 13 weeks. The 1st semester of a foreign language covers 2 years of HS language. Some classes decrease the student’s grade if they’re absent more than 2-3 times per semester, others count participation including in-class quizzes. In short, he can indicate (to his adviser and what dept deals with this at PC) he will need accomodations and try his best to be there for his sibling during breaks but he has to be able to project himself as a college student, not just as a sibling.
Finally, it’s clear PSU is unaffordable and you’re already under a lot of stress. It’s just not possible. The level of stress you’re feeling right now… 
Btw, 1/3 of UMass Amherst would currently be 12k (if a typo and you leant 1/2, itd be 18k) + whatever from the 529. Although no amount was written down, this is a guaranteed amount.