Back button will be fixed (in fact it is already fixed in dev build). The firmware for Bluetooth is included, it should work. Have you tried enabling Bluetooth in LE settings? Also can you give me a result of cat /sys/bus/sdio/devices/*/device && cat /sys/bus/sdio/devices/*/vendor if it doesn't work?
With my X96 (S905X using p212 2g dtb with either 008 or recent dev), enabling Bluetooth returns no adapter found.
The Results of cat /sys/bus/sdio/devices/*/device && cat /sys/bus/sdio/devices/*/vendor provide:
vendor
0x8179
0x024c
Dmesg results link: JRbR if that is also of any use.
Cheers!