olememphis51,
It's fairly common to flip the copper contact in a solenoid starter so my guess is that a stomp style switch would be no different.
If you pushed the starter switch down with your finger and the starter spun, it was doing so under no load. Mashing the pedal in the cab engages the starter drive with the flywheel and closes that little switch. This demands full battery power to spin the engine.
Your battery could be failing or your starter could be failing under a load. It wouldn't be common for the starter drive (little gear) to bind things up. It's more common for them to break internally and spin free. If the disconnect switch your friend had you install isn't large enough, the starter could starve for battery power. This could make it heat up as it tries to turn the engine over.
With a fully charged battery, I would bypass the disconnect switch and see what happens. If your starter was looked at by someone competent, it should be alright. Good luck and keep us posted on this problem.
Stuart
