current values over the slot car controller:
when connected to powered slot car system and at 0% throttle: 0.25mA
when connected to powered slot car system and at 100% throttle: 0.50mA
Quite honestly I don't believe you are making those measurements correctly. They are stupidly small ammounts of current for a slot car to take.
How are you physically making the measurements?
My reading of the data sheet is that the maximum current through the wiper is 2.5mA, this is way way too low to do what you want to do. You have probably blown the device and you are measuring something that is broken. A current of 2.5mA is not going to power your slot car. The whole design of what you want to do is wrong.