I'm happy to report I was mistaken about the proximity sensor... It actually works! I tested it with a phone call and the screen properly turns off when held close to ear and lights up when moved away. (Before I looked the sensor status using AIDA and it is flaky and inconsistent there.)

Phone calls work including speakerphone.

I got the bootloops stopped by removing symlink wlan-module-load.service at /lib/systemd/system/multi-user.target.wants/. (This is the workaround fix by the developer described in at the xdadevelopers thread.)

At this point it is only the camera stuff left?