Root canal or extraction?

One of my molars top left was sensitive due to a hairline crack 5 yrs ago so dentist suggested a crown to be put over. Got a Zirconia crown and all was ok until this past week. The tooth had no root canal then. Just the crown Saturday, while chewing on some fries in that area of the mouth, I felt a bit of an ache momentarily but it went away quickly. Then on Sunday whilst flossing, the crown popped out. Picked it up and saw it had 2 holes on the surface where I chew on. I went to a dentist on Monday to get a new crown made. I thought it would be as simple as that but after he looked at the tooth requiring the new crown, he said it was cracked and using a camera showed me on the monitor the crack going across the molar. He also did an xray and saw the old hairline crack going into the gum. He then proceeded to knock the tooth with a tool and asked if I felt anything and I had none. He said that the nerve was probably dead but I asked how can it be dead if I had an ache when chewing in that area 2 nights ago. He proceeded with some other type of test, which I suspect is running a current onto my tooth since he had a metal hook one end in my mouth and anthr device on my tooth. That's when I felt a sharp pain when the device was turned on. But it stopped when it was turned off or removed. The dentist then informs that I can do a root canal or extraction. As I want to salvage the tooth, I requested for root canal. He anasthised the area and we procced. The dentist drills an access hole and removes and clears out whatever is inside. Then informs that he can see the crack on the tooth from inside. He indicates that if he continues with the root canal, it wld last around 1-3 yrs only and I wld then need to get it extracted. He suggests to extract instead. I didn't expect to be presented with this choice to make so he sealed up the access hole and gave me amoxicillin (250 mg 16 tabs to be taken 3 times per day) and metronidazole (200 mg 16 tabs to be taken 3 times per day) and said to think on which option and go back in a month. So now I've had a pulpectomy (per the bill) and temporary filling that can only last a month over the access hole. My questions: 1) should i opt for the root canal or extraction? 2) i seem to feel sore now at that tooth area 4 days after the pulpectomy, maybe I'm imagining it? I've not taken the painkiller prescribed (paracetemol with codeine phosphate). Only the prescribed antibiotics. 3) should I get dentist to reschedule to get a root canal done sooner instead of waiting till a month to go back? 4) should I get dentist to do an extraction sooner instead of waiting till a month to go back? 5) wldn't the extraction affect the other 2 teeth on each side of it? Can I also lose them eventually? 6)can a denture damage my gum and good teeth that it needs to prop up against? 7) can a root canal be redone? I mean if the dentist is saying it will last around 1-3 yrs.