Regarding the oscillation. Lead dress is CRITICAL with this style of amp. Make sure the presence circuit lead from the impedance switch is routed away from the preamp leads. Make sure grid leads are not longer than they need to be. Make sure OT leads (primary AND secondary) are also not longer than necessary, twisted together and routed away from the preamp.
Regarding the ghost notes. Double check your wiring for the power supply. If the power supply is wired correctly with good working caps it shouldn't ghost. You may have a wiring error that is preventing the necessary filtering and/or decoupling.