I would suggest a chlorine bleach solution, to kill any mold spores. But that might bleach the color of the stock. Then again, given the condition of the stock, that might be OK especially if you are going to stain it anyway.But best to check with a skilled woodworker.
I can feel you pain. But the main thing that the gun shoots like it supposed to. I hope the mold problem can be fixed. I know Jomax is used for mold and mildew for prepping before house painting. As for the metal finish there good paints out there. I was watching American Guns and they use Cera Kote on thier firearms. There is a guy with a post in the GTA that has been using it also. Read a PB forum that a guy painted his gun with engine high heat spray can paint with ceramic. Then oven baked it.