Your description of the pins is very confusing to me. The IC pins are numbered on the voltage chart on page 1 of the troubleshooting guide. It would be very helpful to me if you could list the pin number and then it’s voltage. It’s much easier if you just measure the pins from the top of the board (not the solder side). make sure to use a solid ground point for the black probe of your meter.
If you get 0V on R28, that’s a major problem. The red pad in the volage chart should be 5V. That could explain why you get very low output. Once again, please make sure that voltage reading is correct, with the black probe on a known, solid ground point.
It might be helpful if I could see your board and solder joints. If you could take some detailed, in focus photos of both sides of your board, with special attention shown to the solder joints (even under the pots), I might be able to see something that could be causing the issue.
-Brach