I've done a couple of 16mm ballscrews. Once you've figured out the technique, it's not too bad. I used a very similar technique to what you described.

In my case I was simply reloading the original balls to new ballscrews (don't ask, you can guess) but for older ballscrews apparently you may need to use bigger balls to compensate for wear. But rather like worn machine ways (gibs) or (split) leadscrew nuts, the wear will be greatest where it's been used most, so I don't imagine achieving zero backlash in the middle of travel will be good for movement elsewhere. Sounds as if you were fortunate to be able to replace the balls with new.

Seems you are getting there!