Maybe this will help ... When I needed greater precision, I created a: "New unit..." of measure: "mils".
Go to: Utilities > Options > Units and:
1. Select "New unit..."
2. Give it the name "mils", Abbreviation: "mil", Size: "1000", is equivalent to: "1" "Inches"

You will now see this new Unit of measure appear within the "Unit definition" field. Once there, you can now select your new UOM in the "Page" drop-down field. If you don't like what you created, you can "Delete unit".

Bottom line - you can create the precision you need. Now as for this extending to the snap function, I'd think so but do not know for sure.