To be honest, this happens with root canals sometimes. I would not fire your dentist. I would for sure get this resolved before trying a new one.
It is true that sometimes they can't tell how big a cavity you have until they get in there. And she tried the conservative approach with cleaning to try to save you $700 in case it wasn't really that bad. I have had dentists do this before, and they are good dentists. Thank GOODNESS one of them did it because he was right - I didn't need a root canal after all, and I still have that tooth with a porcelain inlay, and no root canal.
I disagree about the refund, I really do. If she does charge you for another cap, THAT'S when you say you will not pay for more than the one cap. I doubt she will bill you for that. If you have tartar chunks, you should consider getting that cleaned at your next 6 months check-up - tarter can cause gingervitis and eat at your gum line, and you don't want that.
If you want a second opinion, get a copy of your xrays and see another dentist that comes highly recommended and tell him or her that you want a second opinion regarding your dental work. Be honest and tell the new dentist that you aren't trying to "down" your dentist, but this kind of threw you for a loop and you want to know if your mouth is healthy and okay. See what the new dentist says.
Having been in your shoes and not having to actually have a root canal after all, I am seeing it differently than your friends. And honestly, you shouldn't have waited when it continued to hurt. You should have gotten back in there right away because infections spread.
I really hope things get better for you quick - nothing like tooth pain and back pain to make you wish you could just go to sleep til it's over!
All my best,
Dawn