A PhD is something that you pour a lot of time in so you can tell most people "nah, just the_third, that's fine" and a few select people "That's Dr. the_third to you."
I had an art history professor that insisted on being called doctor; she said she'd put in a lot of time and spent a lot of money to get that degree, and so she wanted to get her money's worth.
I was being serious. She made art history--which is normally a fairly dry subject, particularly when you're covering art before 1100CE--a really fun and engaging subject.
No; adjunct faculty can also rightly be called professor without having achieved a doctorate. I've had a few professors that had BAs and MFAs (esp. since I'm not sure that there are PhD programs for fine arts).
Well, actually the “pronoun” would be “The Doctor”. And since it applies in both contexts, it’s applicable to both. However it’s really not a pronoun as much as it’s A unique Proper-noun/noun/pronoun tri-brid.
Basically, it’s all really confusing, we should all just acknowledge this as a Quantum-noun and move on.