My PhD seems daunting and overbearing. How shall I regain motivation and interest?
my supervisor (...) keeps saying she has no concerns


Believe her.

Having lots of comments and suggestions for improvement does not mean she doesn't like what you have done. It may be the exact opposite: because she likes what you have done, she wants to make sure your research is presented in the best possible way, clearly demonstrating its potential and value.

I would suggest taking some time off to recharge your batteries and then working through the list. You've made it this far, now do what it takes to complete your PhD. Judging the value of the research is most likely better done in a less stressful situation (i.e. once your done).