Is it safe to use "baby" orajel on a 6 month old who is teething?

Yes. it is safe, but may not be the most effective remedy. Cold applied to the area, such as chilled teething rings and acetaminophen orally may be more helpful.
Yes. but only a few amount couple of drops each time and no more frequent than 6-8 hr intervals.
Yes. Just follow the instructions and don't apply too often.
It is recommended. There are plenty of tricks (frozen wash cloth, cold spoon,rubber nubby, gel-filled teether, orajel ) to help your baby. If no amount of Tylenol (acetaminophen) and frozen teethers are helping your baby talk to your pediatrician about prescription medication. Good luck.