Try to install this zip through TWRP.
MOB30X from MOB30P
Marshmallow OTA link - https://android.googleapis.com/packages/ota/sony_tetra_tetra/b494dd69f7428b3a79b2d13642c794e2ee74fbab.signed-tetra-MEC24H-from-LCA43.zip
It is possible to do a similar test version kernel as you do for Nexus 5 (with 4.4.3 kernel sources) also for Nexus 7 2013, please?
What am I doing wrong?
Did you use Ext4 partition just for some part of your SD card? I installed this ROM for 2nd time (was changing old and slow SD card for a new one), and its working without any problem.
I make second 4GB partition with ...