The muddle in the middle reminds me a lot of the middle game in chess. Surviving the middle game is a huge hurdle when you're learning to play chess. Thriving in the middle game separates the accidental winners and losers from chess masters, who exploit the chaos as much as possible.
I think writing through the muddle in the middle is really similar. At some point surviving it (rather than taking weird plot turns or losing characterization/plot in a weak and complicated mangle of words) becomes thriving becomes mastering that muddle and turning it to your advantage. I don't feel like I'm really thriving there yet, but this time around I feel like I can see more clearly than I ever have before. It still feels complicated, but my characters and the plot haven't gotten lost.
Nothing to do but plunge onward and see what happens next!