Tooth 14 rock solid in jaw. No pain. Deep sulcus with fistula. Periodontist will extract. Guesses if tooth abscess. Says lesion. Savable?

See an endodontist. for evaluation. Endodontists are dentists who have at least 2-3 years of advanced training in root canals and saving teeth. No matter how effective dental implants are, and they can be very effective, generally nothing is as good as a natural tooth.
Heroic. If the Periodontist thinks it isn't salvageable, go with his/her recommendation. Heroic measures may not be cost effective.