Not been following too closely but FWIW IMHO...

I don't think that's a good guide Scot because the font you are using is
probably proportional so different letters take up different amounts of
space.

I tried something like this for another project where I wanted to fill
simulate columns in a listbox. The best I could do was put the text  into a
hissed textbox set to auto expand and then pick up the width.

It's tricky though because of all of the conversions to and from pixels
points inches cm and so on.