I am totally lost now. I expected you to get around 140V on the screen grids but you have normal voltage there. The filaments voltage is a bit high but not as much as I expected. The screen grid voltage is taken before the field coil directly from the rectifier tube. If the voltage is normal there, how can it be 100 volts higher on the other side of the field coil ? Are you sure about that 358 volts reading on the plates ?