I'm not completely decided yet on whether to continue as is or to rewrite, but I did make the changes I decided on making. Long story short, I changed my mind on the scale. Rather than get into the multi-month-long process of making changes and rewriting the entire book to compensate, I just changed the one fight that really irked me. I left her teleportation alone. With what I have planned for the story, it'll be fine. I've already introduced the counter to it, so it's best left alone. There'd be too many changes if I messed with it, and I know I wouldn't find everywhere it impacts. Long story short, nerfing it would do more harm than good.
Summary of Changes
Change 1: Changes were made to the way Kamui wins her match. Rather than change it so she loses to Yugao as I initially planned, I changed the fight so that Kamui never gave her the chance to take advantage of her superiority at close range. I didn't make Kamui inadequate at close range, just not at an Anbu like Yugao's level, especially since the jonin specializes in it while Kamui's focus is elsewhere.
Change 2: The conversation with the jonin was adjusted to compensate for the changes in Kamui's assessment. I've also added the note that the reason why the human body can be stunted by over exertion at a young age is due to the presence of chakra and alluded to the fact that chakra has only been present in humans for 3000 or so years in this fic. Basically, the human body didn't evolve with it long enough to be perfectly in sync, so it can allow the body to damage itself if not used responsibly at younger, more vulnerable ages.