Kernel Panic broke my iMac

My iMac (late 2012, 27", MacOS X 10.13.3) does not startup properly after a kernel panic. In verbose mode the startup process hangs at one of these lines:

OConsoleUsers: gIOScreenLockState 3, hs 0, bs 0, now 0, sm 0x0

Sound assertion in AppleHDAEngine at line 9502

Setting BTCoex Config: enable_2G:1, profile_2g:0, enable_5G:1, profile_5G:0

The first line is the one where it hangs most. Sometimes the second and third come up right after the gIOScreenLock message.

I can start in single user mode and check and access the hard disk. It does not report any issues. After a few seconds at the root prompt, this is shown: pci pause: SDXC

This message is also shown once when the normal startup procedure is running.

When I try to start from the TimeMachine backup the computer hangs at:

fInterfaceSnapshots is missing

This line is repeated seven times.

The fsck command does not find any problems with the hard drive.

The above mentioned issue also occurs when I start from the recovery partition, from Internet boot, from a full TimeMachine backup, and from an emergency Mac OS X on a USB-stick, which I know that it works.

The only things that work is to start the Apple Hardware test (press D or ALT-D at startup) and Windows 10 in safe modus from the Bootcamp partition. Normal boot of Windows shows the first loading screen with the Windows logo and the circle animation for a short while and then goes completely black (the background light of the screen is turned off). I can hear the HD working, though but nothing is on the screen.

The Apple Hardware test does not report any issues.

I moved all the .kext from /Volumes/MacintoshHD/Library/Extensions into a temporary folder and restarted. The Mac rebuilt the kext cache but it did not help.

I reseted the SMC and the NVRAM with no avail.

I can't boot into Open Firmware with COMMAND+ALT+O+F. Why not?

I started with SHIFT held down. The computer hangs anyway.

I put a live Linux on an USB-stick and started from there. It does not fully boot up.

Is it a hardware problem? I don't have an Apple Genius Bar in reach.

What else can I do? I would wipe the computer and reinstall it from the TimeMachine backup but I can't boot from the backup or any other external source.

Steffen