Problem with "messed up" amps is that we donīt really know whatīs there.
It will probably match no known (or unknown) schematic.
I suggest a longer but safer way to solve both problms: part designations may change but they basically still must be there for the amp to work.
Print a large copy of the schematic, even better if you print it twice the size, in two separate sheets which then you tape together, and go along the board checking parts one by one and annotating the schematic with new part designation and whatīs actually there.
Then take a picture of the corrected schematic and upload it here.
So, for example, you will find that "the cap which goes from V1a cathode to ground" which MUST be there, is labelled, say, "C4" on the printed schematic but "C2" on the PCB and instead of ".1" is actually ".22" or whatever.
Do it at least for the entire Clean channel, from input jack to input of V3a
Does the Dirty channel work fine?
Can you set its gain pot (the dual one) down and get reasonably clean sound there?
Or itīs also splatty gated?