Once you have any perforations like that, new metal is the only way to permanently fix. I would remove the windshield. Sandblast all rusted areas, cutout and weld new sheet metal. Corroseal rust converter treat surrounding metal, prime and paint. I’m in Canada, but I would guess $3k. (US dollars would be less) I just went through a rustoration on my 97 Yukon, and the shop swears by this stuff Corroseal. Converts rust to a black “Magnetite” which doesn’t allow it to continue the electrolytic process it needs to corrode. You could grind the area the best you can and brush some on, until you decide to fix properly.
