Joseph Proscia, DDS

For crowns, once they are made, that is the color you're stuck with.  You can try getting a dental cleaning and see if polishing them brightens them up.  But whitening will not work on crowns.  The only way to whitening them would be to get new crowns.

If the pain from cold lasts longer than 60 seconds after the cold is taken away you may have a nerve issue requiring a root canal.  I would have the dentist take a CBCT (a 3D type of xray) of the area if he has the machine to do it.  Or just a standard xray and check the ends of the roots for infection.  Odds are if it's been hurting this long the nerve is compromised.  It can happen sometimes when you are working really close to the nerve.  Good luck. 

When a crown is placed it should feel like it's been in there forever.  The tooth should not stand out compared to the other teeth.  If you feel like you are touching that tooth first when you close you should go back to the dentist and have him adjust it until it feels like the rest of the teeth.  

For esthetics I would choose emax.  Zirconia tends to be more opaque and less esthetic.  Crowns should feel natural.  If you are banging on a tooth that needs to be fixed asap so you dont damage the tooth or surrounding tissue.  As far as the tooth next to it, you could get braces or invisalign but its a very expensive way to get one tooth straight.  Putting a veneer or crown would straighten it and be more cost effective.

Anything you do in dentistry will have a shelf life.  Crowns and dentures for example have a 10 year average life span.  Fillings usually have a 4-5 year lifespan.  These numbers are just an average.  If you take good care of them with good hygiene and seeing your dentist 2 times a year for cleanings and exams, they will last a lifetime.  Now as far as your situation, either option will work. Bonding is basically a plastic material that bonds to the tooth and fills a void.  It will wear down over time and could pop off due to constant biting forces everyday.  Veneers are basically a mask for your tooth.  They shave the front of your tooth down and glue on a veneer.  You are correct that these have a tendency to pop off because they dont have much physical retention and rely solely on the cement to hold them in.  Crowns are a better option since they have better physical retention as well as the cement.  The only issue with doing crowns or veneers is that the surrounding teeth may not match.  This is why a lot of dentists recommend crowning or veneering the surrounding teeth to match. Hope this helps.