UPDATE:
As bigfred and fietsbob thought, the indexes on the 8-speed shifter are simply too far apart. I only have 3 usable selections: OFF, Barely Touching, and Immovable
Luckily, I ordered some Dia-Compe Silver Bar End Shifters last week which should arrive today or tomorrow.
The product description is as follows:
These are copies of the Suntour Micro ratcheting shifters and one of the best shifters of all time (only the discontinued Simplex retro-friction are slightly nicer). These are the Dia Compe Silver down tube shifters adapted to bar enduse.
Back to work...