We will have to assume that your amp was in good working order and passed its voltage checks prior to you installing the Speedball in order to give sound recommendations.
Assuming that is the case, the presence of 422V in the amp is a surefire indicator that you have a ground wire (black) that is loose or poorly soldered. Take your needlenose pliers and tug on each end of each black wire and see if any of them moves around. The common one that I see that's loose is where the black wires meet on the headphone jack.
A very poor ground connection along that path of black wires will give these odd voltage readings. I wouldn't do anything with/about the small PC board until you see IA and IB voltages that are 200V +/-50V.
