Hello Gary,
Snapping is not available in Spine yet, but the feature has been added to our tracker here:
https://github.com/EsotericSoftware/spine-editor/issues/554
(follow it from GitHub if you want to be alerted of when it will become available)
Regarding different arrow key nudge options, if you press shift you can nudge by one pixel instead.
If you need precise shifting, Spine can also do the math for you:
Tools - Spine User Guide: Numeric entry
Input a plus to add to the current value by the amount you specify, or a +- to subtract.
