Thank you for everyone who replied, it warms my heart to see love for this story even after all these years! Based on your feedback and some of your advice, I have decided to go with a rewrite with a completely new story. Many of you love the original story and enjoy rereading it, so don't worry, I won't erase the old story. You can find the new story under the title "Changing What is to Come (rewrite)":
s/14302256/1/Changing-What-is-to-Come-rewrite
The main reason I decided on this course is that my writing style has changed over the years. It would be much harder to change a few details here and there and continue in a similar style. I also want to make Kakashi more in character and give a more realistic take on how he would handle the situation.
I decided to keep the time he travels as is. Not knowing the full details behind the Fourth Shinobi War will give me more to work with as Kakashi combats the unexpected. I could have gone with the plot of Boruto, but have no interest in that whatsoever. I'd rather stick to the events of the original manga and my original ideas for the fanfiction. Those who told me Kakashi's timeline is screwed up were right, it made my head hurt trying to make sense of it! So I will be following the timeline that makes most sense to me.
Happy Reading!