Being a sphere, the Death Star is 160 km wide from every direction. That’s substantially larger than a flat ship with a 60 km wingspan. Anyway, onscreen it didn’t look that much bigger than the Executor, so I don’t really give a shit what the official numbers are.
Yeah, but the part of the wing the cruiser sliced off like butter was about 20,000 meters wide. The FO Star Destroyers are also quite a bit bigger than the Imperial Star Destroyer. Either way the DS would have sustained major damage, to the point where it would no longer be oeprational, especially if the cruisers had pointed their attack at the DS disc.