I think I've found a way to work it. I've written way more than I need, so I can break at a specific point and have it be a complete story within itself, but with a few loose ends dangling, and those will get taken care of in the next story, which depending on where I break the first time, I'll have already written nearly half of.

And hope to gods the readers don't want to lynch me for splitting it where I'm thinking about.

And edit the crap out of the part I've already gotten written.