Ball supply and other questions

Hi, Trying to re-ball a TBI double nut 32x5mm pitch screw with 260 nominally 1/8" balls while keeping costs down. There was play and some fine metal particles so I pulled it down. The screw and nut look OK under a magnifier, as do the balls. However I wanted to install new balls as the machine is old and there must be some wear. I noted on a previous post a ball supplier Bal-Tec. They seem excellent. They are not dirt cheap because (1) I'd have to guess and buy a range of ball sizes, and (2) they seem to use UPS which to Australia is not cheap for a handful of balls.

As per this previous post here (and the Bal-Tec website) there are indeed two sizes of balls in my screw approx 1 thou difference in size (that'll be fun re-balling).

I've got few questions;

1. Is there other quality ball suppliers?
2. I assume one would ideally like the nuts to be close to a preload condition when reassembled without nut preload?? Is that correct?
3. Is there a way to get some idea of the wear e.g. Reassemble the old system without preload and feel?? Try and measure (indicate) radial movement, not easy and some complex geometry in the
ball contact to come up with a new ball size.
4. The other method which is obviously used is trail and error (probably the best method) but what sizes to try given the costs of buying many ball sets. Try + 1, 2 & 3 thou?? Does someone have
some experience and could help with a 0better guess

Thanks