2. Poor oral hygiene is what causes tooth decay. Extensive decay will cause tooth sensitivity.
3. A good oral exam should pinpoint the cause of your tooth sensitivity.
One, I do believe that Novocaine is no longer commercially available. I believe Septocaine is the most commonly used anaesthetic. There is no problem requesting and using an anaesthetic.
Two, if sensitivity is the concern with the teeth consider using a shock absorbing nightguard.