For item #2 your SOL. Unless you have an existing nand/nor dump from that specific console before 3.56 was flashed to it you wont be able downgrade it.
Originally Posted by KingOfRochester
For item #1 ... It sounds like an issue a service mode dongle might be able to fix. Hopefully someone else can weigh in with more info since I've got very little experience with trying to fix a RSOD.
CECH-G01 PS3 fat -- 160GB -- 3.55MFW (PS3MFW v0.2)
CECH-2501B PS3 slim -- 250GB -- 3.55MFW (PS3MFW v0.2)