just got one that got assembled badly. As for the sight, the barrel has a flat milled into the muzzle end that the sight key's into. So don't try to twist it.The barrel might just be twisted in the breech, but to check that you will have to take the breech off and make sure that the transfer hole in the barrel is centered in the breech hole. It just might need to get re adjusted.
The gas going out the barrel is a valve issue, either intermittent debris getting under the stem seal, or just a bad valve.
You can easily take care of these issues, but you shouldn't have to. Send it back and have them deal with it.