You don't have to pull the pump.
Just unbolt the driveshaft from the crank pulley.
You can move it enough to fit the belt(s) through.

As for the throttle cable, I think you are on the right track...
If you already ran a ground strap to the engine, then I'd say the chassis needs a better ground.
The neg. cable should attach to the engine first. Then the ground strap just has to handle the current from the dash and lights.