Now this seems very low. Is this with a reservoir ecap connected??I am getting about 338 VDC
I don't think it is possible to produce a negative voltage from a HT tap when using a bridge rectifier, so your proposal won't work.
I just saw that there is a BJT stage that requires a -32V supply. So while full cathode bias would provide a solution for the power stage, I think you need a different PT that allows for the -50V supply.