800k minimum balance is 2 months before and 3 months after initial 1 yr extension. No health insurance requirements or criminal record checks for Non Imm O, that is for OA.
you'll only be stamped on till Jun 2nd. If you haven't already applied for a 30 day extension you can buy one when you return to allow you to stay until July 1st or so.
not really possible to know how immigration will deal with extensions for this visa in September. We don’t even know if the program will be extended. Right now at a minimum it’s a viable option for around a six month stay whether you’re currently in the country or planning to buy one in your home country and travel here.