Yeah, what is your objective to adding the volume on the input? That is the same as your guitars volume control.

  I would put a dual 470k volume on the 8k2/470k junctions for each EL84. That would let you turn up the pre-amp and still have a lower volume out while driving the two 12ax7's into distortion, if that's what your after, often called a Master Volume.

C32 would be suspect, also C33&34. It seems U7 has somehow become unstable in the high frequency range.