ISTM that you should be calculating your fuel for departure from Point B and subsequent payload: not from Point A.
Add 2 gallons for startup/shutdown.
Total fuel required is 20.3 gallons.
Of which you will have burnt off 7.7 gallons flying to Point B, plus 1 gallon of the startup/shutdown allowance. Further, you will use the second 1 gallon allowance prior to take off from Point B, so your fuel
on takeoff from Point B should be 20.3 - 7.7 - 2 = 10.6 gallons.
Minimum fuel for the return leg is 10.7 gallons, so you need 20.4 on departure from point A. Pt B departure fuel of 10.7 gallons would be 64.2lbs.
The payload available will then be 215.8lb, or 19.62 bars.
If the R22B has an aux fuel tank, minimum pilot weight is 135lb, so an extra 5lbs ballast would have to be carried on both legs, reducing the payload accordingly unless the outbound ballast is discarded and replaced with bullion for the return leg
