Please hel - root canals, extractions and more

[TerrifiedinToronto]

At the beginning of January, I visited a new dentist (Dr. X) because of pain I was having on my lower left side. Dr. X performed a test by inserting a metal prod into the gum, and indicated that because it went X mm deep, the tooth (#36) had a verticle fracture and had to be removed.
I returned to my old dentist (Dr. Y), who I had started to distrust, but who had performed a root canal on this tooth a couple years ago, ensuring me that he had built up the tooth enough that it wouldn’t warrant a crown in the near future. Because I am student/artist, I subscribed and left the tooth as is. When he saw me, he said there was nothing wrong with the tooth and I simply needed that crown.
At that point, I returned to the Dr. X wherein their periodontist saw me and confirmed that she believed it was fractured and required extraction. After getting a third opinion from an endodontist, I had the tooth removed and did not return to the Dr. Y. (The side-story of his recapitulation, or rather his secretary’s phone call, said that after getting a letter from the Dr. X's periodontist, he now thought the tooth needed extraction – no re-examination, no consultation. My worst fears of him being a crook were confirmed.)
I had a lovely oral surgeon perform the extraction, and though it was healing well, was still experiencing pain in the area. In order to ensure that the teeth around it would remain in good condition so I could get a Maryland bridge put in (still the issue of lack of finances), I returned to Dr. X who had referred me to her periodontist and then to the oral surgeon for a minor filling on the farthermost molar (to the left of #36).

[TerrifiedinToronto]

A couple weeks later, after several consultations with the oral surgeon and still having pain, I returned citing problems which had developed in response to hot and cold liquids. I thought at the time it was the extraction site, but after referring me to her endodontist and a cold/hot test, he indicated that I needed a root canal on this farthermost molar.
I returned to Dr. X who I had seen originally and who had performed the filling, because the endodontist suggested it was likely a cause of the filling. She looked at the xray and, truthfully, the filling was very shallow and not close to the root. It then occurred to her that I might grind my teeth – and in the process have harmed the nerve, requiring a root canal on that tooth. Moreover, I am also experiencing sensitivity on the tooth to the right of #36, and on a tooth above which had a deep filling done about a year ago.
I am waiting to go to a sleep lab to see if I have sleep apnea before they perform a root canal. However, as you can imagine, I am very frustrated and confused.
1) Does it make sense that the nerve could be permanently damaged simply from grinding?
2) What steps can I take to ensure that the other teeth in the area don’t require root canals?
3) The dentist told me that the root canal is only imminent because of the pain. However, I am now terrified of a tooth extraction and wondering if there reaches a point where the root canal could lead to requiring an extraction, or am I good to wait and see if the nerve settles down (as she suggested)?
Any advice you can provide would be most appreciated.

[Jerome Tsang, DDS]

Sorry to hear you're having a hard time with your teeth.

Well its hard for me to figure out exactly cause I'm basing it off what was said by each dentist/specialist.  My personal opinion on the matter based upon what you said is this:

After the root canal, the back molar most likely should've gotten a crown done to prevent a possible fracture.  

As for the pain remaining after the extraction, which I do agree as a reasonable treatment given that it already had a root canal treatment and if the probing depths are significant, it can indicate a deep fracture that's non-restorable, I'm not sure why there's still pain.

So, my question is, is the pain still the same or is it a different kind of pain?  What was the original pain like and what is the current pain like in terms of quality, such as throbbing, burning, stabbing, spontaneous, intermittent, constant, when you chew, exposure to hot, cold, on a scale of 1/10, is the pain isolated to just the tooth area or does it spread to other areas?  When does the pain start or stop? What triggers it?  Does it change throughout the day?  Etc.