This radio looks to be one of those "sequence of events" which means there is more than one thing wrong in any given strip in the radio.
So look for fresh solder and "type cast - compare" radios side to side, if at all possible, to narrow down the spots in the strip that need further investigation - fresh signs of previous work is a good clue to this.
You look like you found one spot, that when you "turned down" one part of the strip - it started to sound better - it's not a boomer yet, but you do have progress. So, work the next stage - onto the next stage - usually when the scope shows good, it's only to a point that it can be trusted - so the rest of the effort is in locating that (GOSH DARN) restriction - because once you see a good scope - means you cleared up a condition - but you might have to return to this spot once the problems were corrected - to restore original levels.
So far, with this progress, my experiences in "crunchy" audio effects, has been where the Pre-driver and Driver are - it's the biasing in both that if one is set too high - a lot of power has to get pushed into it, to even get anything out. IT doesn't get amplified very well either - no dynamic range.
IN the radio your next stage is the Pre-Driver so the focus then becomes; on stabilizing the driver - make sure its' area looks clean and all the caps and resistors are seated - any carbon traces or solder "hairs" in here can wreck your efforts.
Carefully measure the Pre-Drivers bias voltages - a few tenths off may signal bad parts or misaligned output core-coil (that bi-filar wind) - again, look for fresh work - I've got top and bottom of the "10" version of that board for you to review the solder mask and component side layouts in this thread. You can always "right click" on the page box numbers and open the previous pages in a separate tab on your browser so you can scroll to the area and review it as needed using CTRL+TAB to swap between the tabs.
