Change your wiring harness.
All of your symptoms could be due to a bad wiring harness.
The insulation is alread brittle and falling off, so you know it is bad, and it will have to be replaced.
You must replace the wiring harness before you can diagnose anything else.
The throttle actuator is a part that does go bad. The throttle actuator also has a harness that goes bad due to bad insulation.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".