Good luck with this! I hope your editor has some great suggestions. Backing out changes is terrible, because of course, you want to keep all the GOOD changes, but now some of them make no sense for motivation or plot development. And you're not the same person you were 2 years ago, so you can't just pick up the issues and conflicts that mattered to you then, and plunk them into the story you have now. They're not what your soul burns to write.