Now that it's getting close to Thanksgiving, we're running a contest to hear advice you've received that you're most thankful for! This can be any type of advice and the advice with the most reactions will win!
I would err on side of caution, regardless of actual credentials. I just used Dr. in all my correspondence to RPDs during applications and it worked out fine.
For supplemental, first see if they have specifics they want. Otherwise, since it's submitted through PhorCAS, I would just header it with appropriate identifiers. Name, place of education, title, whatever else you feel is needed).