Fastrax review and alignment questions for the pros.

The Direct Connection Oval Track book has a graphic converting toe degree to toe distance based on tire diameter. Figure 124-35

The shop manuals make the procedure pretty straightforward.
I have three caster/camber tools, one toe gage and have also used strings. Any measurements need to be from a reliable surface. The only way to use the tires for final toe is marking the tread. Outside of tires are too variable, although as long as you're consistant, its fine for quick and dirty approximation. Sometimes thats enough.

I have the Smart camber digital. Its similar to yours, except no toe extensions. I hold it in place to take the caster and camber degrees. Without marked plates, I just use consistant number of turns on the streering wheel for caster. As far as digital vs. spirit level - I'm with you - spirit level is my preference. Only advantage to digital is the ability to zero out inclinations in the floor. That's still not correcting for the fact that the floor isn't level (as the chassis is still reacting to the slope) so its not really a plus.

Following rutts and related highway wander is toe out while moving. Talking 60 mph here, not 95 + mph.