1. Try a discuss. Also, it may be based upon % in fervor and not in essence of faith, just because I would think a commune edge would not be virtue dependent. I had the edge with my last pally, but I can't remember when I took it, but I think it was before I got the faith virtue.

2. I don't know that you'll get an exact % answer, but probably better just because you are fighting unarmed so more armor deflections is probably beneficial.

3. Dupmasione, Thendrell, Sarien & Unalethekai are about the only ones I know of for sure that had 3 virtues, and they were all in the fourth age. Nobody in the fifth age to my knowledge has done it. It is generally rare and given to characters that have been around a while with a decent presence.

Lariya, Niheriva and Solasarath also had three.

Yeah, I wasn't playing back then, so I just went with ones that were active while I was playing.
I am sure there have been a few others, but looking over the span of time the virtue system has been in place compared to pallys rolled in that period compared to ones that got three virtues I would say it is less than 2-3%. Or maybe 2-3 a year.

Have you tried Discuss Prereq? That command should help you find out if you can ever pick that edge or what is required.

Unsure about the armor edge but it would make since as armor I could imagine would pay a stronger role when not using a weapon.

and Yes but it isn't common.