One of my old S2's rotted in exactly the same places mate

Roof was every bit as bad as yours and drivers side rear wing just below the window edge was prob worse than yours !!!! Ended up just filling the roofskin and managed to cut out and replace the top section of the rear wing, used plenty of rust treatment and the roof repair lasted for a good few years before the car was eventually scrapped

Shell is def worth saving yet mate if you are keen enough and patient enough to repair it