Just take the trouble to mount your worm in an eccentric bearing housing. This lets you either disengage the worm completely from the gear whilst dialing in your workpiece, or, allows you to snug the worm as tightly into the gear as it can possibly fit. You might even run it a while with some lapping compound on the gear teeth to take off any high spots.
Software backlash compensation is not likely to be satisfactory: your milling cutter will cause the work to jitter even while the rotary axis has no motion command to execute. Backlash comp only works for motion reversals.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)