Looking at my story map, I can see a massive drop from chapters 1 to 2 in terms of views. And chapter 1 is very long. I'm about nine chapters into a linear story. Should I split chapter 1 into two parts? And if I did, how would I put a new chapter in between chapters 1 and 2?
The stats on your story aren't really high enough to warrant that kind of analysis yet. Regardless, it is pretty much inevitable that your first chapter will have several times as many views as your second. This is because the views aren't unique, nor are they guaranteed to be human. Whenever someone accesses your story, they're leaving at least one view on the Introduction chapter, unless they access it directly by story map or via another chapter, both of which are quite unusual. This includes yourself. Additionally, things like search engines might trigger views on your Introduction chapter. Views are almost meaningless, and certainly shouldn't be used to make decisions like this.
If you want to use stats to inform your writing, I would, for now, pay attention to your likes. You have distinct peaks at chapters 1, 5, and 8, which actually implies two things: firstly, that people who read and enjoy your first chapter are highly likely to continue onto at least the fifth chapter (as they have equal likes); secondly, there is something specific about each of those chapters that stands out to your audience. You could figure out what you've done well in those chapters and try to do it more often.
To answer your question directly, while 2600 words is very long for a CHYOA chapter, especially for an introduction, it is not currently possible in the system to split or insert chapters in the way you describe. You would need to delete all but the first of your chapters and copy them over to a new branch with the extra chapter added in. I don't believe it's necessary at all, but if you feel strongly enough about it I would recommend doing it now while you have less readers to confuse and less stats to lose.