How much rust is too much?

Since you didn't want the it's your car ... thing, I voted to part it out. That said, I'm resurrecting two rust buckets. The 4-door had floor issues which were easily fixed. Grind/cut out rust, fit new panel, & weld.

The Demon had roof rust similar to yours. There was no rust at the lower part of the glass, but the roof and A-pilars were disasters. The A-pilar damage is structural, so no re-skin is going to fix it. I had a great, old-school coach get me through decapitating the Demon and a donor car. It is nerve wracking to cut and time consuming to shape and re-align the panels for re-attachment. If you get it wrong, the glass does not fit properly.