How bad did I #$&% my piston up?

If you can borrow a ring gap filer from someone, do it. File only one end of a ring, not both ends. That will help you keep it square. Stop when you hit .026". It's not the end of the world if you go accidently go beyond that - just be careful. Remove any burrs from the end that you file.

The machinest should have used the pistons and final honed the cylinders to reach the piston to wall clearance that KB recommends. The hypers can run tighter clearances than the forged or other pieces.