when you calibrate the slide axis in AH2 make sure you leave it near the middle when finished (does not have to be exact, just close) and then your slide will give you full zoom range. I use my x52 precision slide for this also and love it. One additional hint, i added about 20% damping on mine, that way there is a little delay, without the damping it was two fast compared to the old key press zoom.
And when you map the Gun zoom to the slide access it is normal for the keyboard keys to not respond. Any time you map a function to an axis you loose keyboard control of that function.