I know you asked for gedollim but if you have medical shaylos i reccomend reading “the little book for big worries” by rabbi yy rubinstein. He lists many orginazations and people to contact for help in the back of the book.
By the way the book is geared towards the people dealing with a loved one being sick, and not just for the sick person themselves.
Rabbi YY Rubinstein is also very reachable and deals with these type of cases often as he unfortunately lost his wife from cancer and speaks a lot about dealing with suffering etc.
Best of luck and stay strong!