That unit is likely beyond help and no one can fix it and certainly not you with a multi meter.
I can not find a service manual. That unit is into the age of the chips with everything era.
The older ones with discrete components are a much easier proposition. Th chance of running into a blown IC NLA a long time ago is high.
From your story I expect a speaker wire got pulled and caused a short. This has likely really blown up an output stage. Your description sounds like the unit is going into protection most likely because an output stage has blown causing a short on the power rails causing the shut down. This would explain the lack of voltage at the fuses you describe.
I think you need to get over this unit and move on. Give it a decent burial.