Sandra M. Low, DMD

Without a photo I am assuming the reflection of your abutment makes the crown grey. One solution is you can remove the crown, mask the color of the abutment, then replace crown. 

Increasing the 2 side teeth is the quickest and cost effective way to get you where you want to be. You can do this with white fillings but better yet if your budget allows 2 veneers. Braces can also help but requires time.

Yes this can be done in one visit, and perhaps you can also use your existing denture which can be adjusted in the same sitting.

The best treatment for you would be a combination of braces and resin bonding since you are still at school. It is possible to close this with veneers in the future when more financially stable.

Yes, absolutely but if you bond 8 or 10 your smile would be even better! Your decision for 8 or 10 would depend on the extent of your smile.