/diy/ - Do It Yourself

I bought a TIG welder pedal, like this one:
https://www.ebay.com/itm/TIG-Foot-Control-Pedal-7pin-connector-For-ATPW524-ATPW522-TIG200P-WSME-CT-Welder/232859854931

It works, but it has a weird intended/unintended behavior. Pic related is how it's wired up, the right pot is the foot pedal control with a 2k pot, and the adjustment knob is the left one with two wires, 10k.

What happens is that the adjustment knob(R2) alters the minimum amps on the welder, and the foot pedal(R1) works relative to it. For example, at 10%R2, I get a minimum of about 30A on the welder, and a maximum of 32A. This is completely useless. At 60% R2 I get 60A min, 80A max. At 100% R2 I get 120A min, 250A max. This is without touching the welder itself, welder being set to minimum current.

What I'd want to happen is using R2 to limit the current range, but not changing the minimum current at all. So if I set R2 to 10%, I get 10A-20A, if I set it to 50%, I get 10A-100A, and so on.
Can this be done relatively easily with passive hardware only? I thought about doing it with an Arduino and either PWM or a digital pot, which would also have the advantage of custom range mapping, but if I can keep it simple I'd rather go with passives.