Automatic Toolchanger not storing tool data persistently and other errors

You haven't wasted your time getting the ATC working (ish) in Axis.  Best to start with a simple GUI and prove the hardware before complicating things with a fussy GUI.

If you're really interested in PP, I'd throw up the bat-signal in the PP sub-forum and see if anyone has managed to get a non-Tormach ATC working.

And regarding Probe Basic, what you do with carousel.comp depends on your ATC hardware.  As I mentioned earlier, while the standard PB ATC scheme doesn't use carousel.comp, there are some workarounds that do - including mine.

What ATC hardware do you have?  i.e. platter motor and control, sensors present (or possible), ATC movement, etc.

Pretty sure based on the descriptions I've read the standard PB ATC will work - I have a carousel with geneva mechanism with index and pulse signals. I have thrown up a signal in the PP forum, it doesn't seem like anyone is actually successfully running PP 2.10 on non-tormach hardware.

Yep, you should be in good shape with that ATC hardware.  Standard subroutines will work, with some editing depending if the number of pockets matches the sim.

You'll also need to manually add variables to your linuxcnc.vars file if your pocket count doesn't match the sim.

I'd also reach out the the PB Devs (Lcvette) here or on GH as I think there's a push to re-write the subroutines and consolidate a bunch of duplicate/superfluous files, as well as generally clean up the ATC & probing stuff.  Prolly a good idea to see where they're headed with that and if it makes sense to use 'beta' configs/schemes they're working on.