What you need is an older scan tool that will let you read the sensors live. I have several of them that I have accumulated over the years.
The codes you list are hard faults. That means that they are present at the time of the test. It sounds as if you have a bigger problem with wiring harnesses and connectors. I might suggest that you start by unplugging them one at a time and looking for corrosion, broken wires, and pushed out terminals.
You are correct in that codes are not erasable as they are in OBD2. As I think about it, it occurs to me that your Vref (reference voltage) is not right. The system (sensors mainly) operate on a 5-volt reference voltage. Actuators usually operate on 12 volts. I would start by checking Vref on the TP sensor first, and then on the MAP sensor. If there is a discrepancy, trace back to the ECM and check for a corroded, pushed out, or broken connector or terminal.