Neda Goharkhay, DDS

It would be nice if you can put the crown back on with the temporary glue. The over-the-counter glue is usually a very weak glue and comes off easily. It would keep the tooth covered and the bite would be stable. Since the tooth had a root canal, there won't be any pain. Be cautious not to chew on it whether you put the crown back on or not. You don't want to put any pressure on the tooth that can break it!

Minimal reshaping of the teeth might be ok but I would definitely consider orthodontics to get them properly aligned for best cosmetic results. 

The gap in the picture doesn't look too severe. You can get a very close estimate of treatment time by having impressions and records taken of your upper and lower teeth. If you would want to close the gap in front and not have other gaps open up, all teeth need to be considered and fit together! Good luck.

It looks like you should have your bite checked and corrected first. If you just bond the teeth to make them longer, your poor bite will cause the bonding to wear down or break off.

You might be a good candidate for Invisalign treatment to move the teeth together without making any changes to the them. Bonding and veneers are also other options. Talk to a dentist to determine what is best for you and get the pros and cons to different options