Sounds like a nice car overall. Everything you list falls into the category of 116 headaches... so fix that stuff and you're off to the races (at least as far as my memory of my '79 SD goes).
Big yell out on the clean windows. Truly a bonus on those cars.
I disagree with you about the sunroof, tho
Check the driver's footwell underneath the dead pedal and behind/around the driver's seat rear mounting points for rust.
Red servo MAY mean it's out of 107 but someone else will need to confirm that.
Defrost-only mode is a separate, fail-safe circuit that operates independent of the rest of the cc system.