RE: Engine, back plate troubles
The 2/56 rod ends wires are quite large and if you use those its not even neccessary to use the outside plastic tubing. Just a small hole through the firewall and the #1 bulkhead. Its only neccessary to make sure the rod does not rub on the fuel tank.
And yes there should be no resistance from the rod and very little from the throttle barrell/arm.
John