They added an exception to the "posession of a firearm with obsured serial numbers assumes attempts to obsure serial numbers" for micro-stamping. So, posession is not proof of intent.
I'm not sure about the durability of micro-stamping. I've seen some claims that they're in the 20-30k rounds range. Assuming you don't run a jewelers stone over the face of the firing pin.
How many dry fires against a hardened steel snap cap would it take?