AGNZ

For AWD your best to keep all 4 tyres same size so they dont effect the AWD system.

255 on 17x8 they will fit but will have slightly lower cornering performance, and looks bad(in a bad way)

Possibly one of the discs inside the adjustable piston is seized.

Try look for the series numbers on the springs. Wipe the dust off first. Usually you could tell from the springs. If you just got them fitted or just got the car. Its very likely the springs are just too hard.