Your chromed bumpers and homemade exhaust pipes came out great. The cast pipe is so pitted, I cant's see it being a viable option without a lot of work.
For the glass issue, I would go through the polishing process to remove as much of the scratch as you can, then a dip into Pledge. Hopefully that will help.
Unfortunately it is not so much a scratch as a molding flaw i.e. it goes always through the plastic. I guess when they pumped the liquid into the molds there must a been a pause hence you get that semi circle below the attachment point. It's not that noticeable but annoying once you do.
Hopefully a quick bath in Pledge will do the trick.