[RedArrow]

Unfortunately sitting is never a good thing even if the car was in a garage. The windshield leak is a possibility but also check on the vent holes on the left side of the clutch pedal.. On my car this area got glued up and fully blocked. maybe it leaked? idk. I like that option as 4th pedal bc in the summer it feels good to have air circulating down there....

Don't trust the numbers of a compression test unless factory spec clearances were achieved first by a fresh valve adjustment.
Step by step, try to check and double check everything. Do you have the Greenbook for the d24?

It`s a 1982, do you have sunroof? Check things around all of the holes in the firewall where wires and `hoses` go through grommets. I would also clean out, flush and gently blow air thru the sunroof drains.. and then, if possible, try to park the car on level ground if possible and keep checking. Pick carpets out, all of them, fully, I am sure there must be some real damage there bc PO had a very steep driveway and that doesnt help with drainage. I also noticed in his pictures that the entire right side door panel was visibly very moldy. Signs of water entering the cabin, I am sure you want to check all of that out sooner or later. That dark blue striped rare interior deserves the best care possible. Rare, comfy, stylish. Our 1978 244 had that, everyone loved it, a true favourite in the 240s.