-- Appreciate you sharing your work with the device tree and kernel. I'm working on getting AOSP 7.0 running on the flo as well.
Can I ask what you are using for proprietary files? Just a standard set from Marshmallow, or did you need to make any substitutions? What about other repos, would it be possible to have a list of the QC stuff you used for the build, or even a look at your build manifest?
My efforts are going to progress a lot slower than yours, but once I get a build running on the device, I will look at the audio issue as well (if that is still current at that point).