Dentist Needs to Make More Than 2 Crowns??

I have been really frustrated and helpless about my dental work.
My dentist did a crown work for me due to cracked tooth syndrome.
No root canal was done since my tooth was tested with cold and the nerves reacted normally.
I went in the second week of april and had the tooth grinded to a dwarf size, then the dentist left me to his assistant to prep the tooth and also had the assistant take the impression. My gum was hurting for a week after that. When I went in for the permanent crown 3 weeks later, the assistant was the one adjusting the crown for me and almost grinded my upper tooth since I kept hitting the crown before my other teeth (the crown is for the bottom tooth). When the dentist came to see me to glue the crown, he said that the margin was not good/not closed at one spot so he had me redo the whole process. I had to go in a week after that to take the impression for the second crown. I told him however to have him do it rather than his assistant which he did. Then I just went in again today, two weeks later after the second impression, to have the permanent crown put in. Again, the margin of the new crown is not closed at the same spot. He told me to go back to redo the whole thing again and mentioned something about the possibility of polishing/smoothing out the tooth next to the one needing crown to fix this margin thing.

I am sorry if this is a long message, but I am just so worried and upset right now.
Can anybody share some insights pleasssseeee.....Appreciate any help...
My concerns are if it's harmful to have the temporary crowns for months?? (will be 2 months).
Will it create any trauma to the tooth and gum with the repeating impressions and adjustment?? (he needs to give me injections for the impressions)
should I go back or should I find another dentist? Will the insurance pay?