Hi Robert
I'm sorry to hear you're having problems with FoCal.
Firstly, the largest and smallest targets are not recognised by the currently released version of FoCal for Target Setup or Target Optimisation. Support for these targets has been added in the next release which is due out at the end of January.
Having said that, you should still be able to run a calibration with the larger target and your lenses. I would suggest you turn Target Validation to off and use the larger target, visually checking through the viewfinder that the centre focal point is aimed at the centre of the target. At the distances you are talking about, slight offsets from parallel will have less of an affect that closer, so it should not be an issue.
Could you let me know if using the larger target in this mode stops the inconsistent behaviour? If not, then it may be good to capture some debug logs, and I can explain how to do that.
Kind regards