Conflicting guitar effect pedals...?

Hi! It sounds like you may have an impedance mismatch with your effects loop in adding the Dunlop pedal. Some amplifiers have the ability to switch effect loop levels; however, the Peavey ValveKing 212 Combo has a fixed “buffered” effects loop intended for low-level equipment. Try connecting the pedal between the guitar and the input jack, which is typically where wah effects are placed. I know from a wiring standpoint this is more trouble, but at least you will have isolated the problem. You may even find that running the entire effects chain between the guitar and input jack sounds better, and could also eliminate the feedback issue. Your effects chain looks fine, although you may want to try placing the whammy in front of the delay. That way, you are not altering the pitch of the delay with the whammy pedal, only the primary effects-processed signal. Best regards, Dana