Vicki Borowski, DDS

I really suggest you start with braces. Your teeth would need to be aggressively prepared for veneers. After the braces if you feel you are still interested in veneers your outcome will be much better. 

It is not uncommon for teeth that have had root canals to turn dark. This does not usually happen immediately.Your dentist can take steps to try to keep the grey line from happening by using a more opaque porcelain.

It sounds as if the post has come out of the teeth . If this is the case it may be able to be recemented. There could also be additional problems but without an xray it's impossible to say. If you are concerned I suggest going to another dentist in your area. 

This is not a case for a 6 unit bridge. My first treatment plan would be and implant/crown in the extracted site, crown lengthening on the other front theeth and veneers. If an implant isn't possible crown lengthening the front teeth then veneers and a 3 unit bridge. 

The uneven gumline should have been addressed before the crowns were done.I suggest meeting with your dentist to discuss your options. These restorations are meant to last a long time so if you are unhappy I would bring it up.