Cake,
We don't want the edge too thin prior to heat treat but in your case once it's heat treated it might take more time to file thinner.
Even a relatively inexpensive Dial Caliper will get a good edge thickness measurement.
Be aware that any ok micrometer has carbide tipped surfaces on the anvil and spindle. This will always scratch a blade where measured, even if just a little bit.
Edited to add:
Dial Calipers don't work very well (ever again) after they free fall to the concrete. This is not theory.
Edited again to add:
With the CPM steels any edge thickness under about .025 (thousands of an inch) is in the risk zone.
What we are risking is warp or bend in the edge that cannot be corrected.
All heat treating here is by me with the exception of the Spartan blades I grind.
The Spartans are sent out to a pretty state of the art heat treat facility that has great control over the process with very good results.
I just measured a couple CPM S-30 VN blades recently heat treated here.
Edge thickness was down at .017 (thousandths of an inch) and they came out straight, luckily. This is risky shop practice.
The "N" in this alloy stands for Niobium.