The brake hone works, seen that solution centuries of years ago. Another way to fix your problem is to find a smaller diameter seatpost and put sand paper around, will take longer but at least you will be sure it is rounded. Use a digital caliper to be sure when to stop.

Probably by respect to the guy you wont tell us who is it, but some of the stuff is fixable, the rear end is pretty easy to do, you just need 135 mm axle, cones and washers. The decals no idea if you have them over the clear or not so it depends.

If the paint job is bad and the light reflextion is bad you have to sand the paint job and polish it. Not many Powder coaters do that, specially if the job is not expensive.

Hope this helps.