Volume control, using opto couplers, nead help to calculation.

[FriedMule]

Hi I am trying to build a volume control that controls two opto couplers per channel.The two opto couplers have to work in reverce of each other, to maintain impedance.

I have copied the 1A current source that Dave designed in one of his videos. The volume control is slammed together by me, so I hope it works.
Each side is a copy of the other. I have tried to build a current divider to be amble to adjust from 0.1uA to 50uA while still having a larger current to run trough the pot. The second pot on the current divider is a multi turn that can be adjusted by a screw, it's for fine adjusting the exactly value needed.

I know the formula for the current divider, but I do get lost when I try to calculate what happens, what values I get when turning on the volume control. Also how much current to run, the Dave-design, gives 1A.