At 55 years of age can my teeth still be whiter? I was a smoker 24 years ago. (Photos)

You can attempt to whiten your dentin first. A little may improve but not enough will make you satisfied for long term. Lumineers veneers without prepping your tooth away more will be best option to achieve that brightness and to protect your teeth.

It is not unusual to have pain after in office whitening. In addition to what you are doing, I would try rubbing some sensydyne toothpaste 2x daily on the sore area and don't rinse or drink for 30 minutes.

I have found most of the time that calcification spots tend to get whiter with teeth bleaching. That being said, there are other options such as post bleaching bonding or MI paste.

You need to see a regular dentist to first get the cavities taken care of. Then you can address the cosmetic issues of possibly bonding the front teeth and then orthodontics. Good Luck.

The bleaching did not cause damage to your enamel.  Many people have these craze lines.  If they are now causing you pain consider porcelain veneers.  Good luck.  

I usually whiten whatever shows when the patient smiles. You can discuss your concerns with your dentist. You may consider having take home trays made to whiten at home. You can add whitening gel to the tray as far back as you would like.