It sounds like you need some distance. Sometimes when you're in the middle of writing your book (or drawing a comic for that matter), it's easy to overlook these sorts of errors; you've just been looking at it for so many exhausting hours of work that you can't see the problems any more. Happens even to professionals, it's why editors exist. In my day job, I help make books, and it's just a commonly agreed fact that you'll never send the first edition to print without at least one typo slipping through no matter how many people look at it! 
My advice: treat this as an early draft. Thank the person for the review, be polite, tell them you'll take it on board, and just keep going, being mindful of the things they brought up. Don't bother going back right now if you can't find the issues, it'll only make you lose momentum.
Then after you complete the work, take a break to do some reading, research or training and start something new. Only revisit this work after you've had a good, long break from it and can look at it with fresh eyes. You'll suddenly see all the issues, and be able to tell which are really there and which were unreasonable nitpicks or fabrications. If you feel like you need to edit the text, you can do it then, or you can just leave it as your "old work" and focus on the new and say "hey, I was young and inexperienced! My new work is better because of the mistakes I made in this older one!". It's up to you really.