It's always nice when that "Aha!" moment comes. I took a little time away from the JASPER novel and then spent a little time thinking and sketching some notes for the rewrite, then I let those notes sit, and then again I sat down after rereading those notes and thought some more and the "Aha!" moment struck. During that moment of great clarity, I managed to establish about ten key points that will guide me in the rewrite. These ideas count as course corrections, bringing the story back on track where I wasn't sure before. The ten key points mostly affect the characters' attitudes and motivations, which in turn drive the way the final events unfold, keeping them much more consistent with the rest of the story. In other words, "Aha!"
Now that I can see the answers that I was seeking before, the lack of which caused me such consternation during those final chapters, I can't help but feel it's all so much simpler than I was thinking it would be. That's one sign that I have the right answers. You know you're on the right track when things fit seemlessly together and feel right with very little trouble.
Now I'll move on to the rewrite. I wasn't sure if I'd go back and do some of the major work first, then fine tune, or just go through in sequence and fix the problems as they appear, whether large or small. I decided I should go through in sequence, to help ensure the logical flow and catch any other things which I haven't already settled with my ten key points.
I don't know how long the editing will take. I'll shoot for a month, knowing it might well be two, but it shouldn't take six months or another year. Half the story is already significantly edited and refined and totally on track. The other half needs some work, but only a few chapters out of 25 are in need of actual rewriting. So, as long as the answers remain clear to me as they did in the "Aha!" moment, the rewrite should not be too much trouble.