[Q] Installed F320S rom on D802, now I can't get back to D802 rom. topic

TL;DR: My D802 thinks it's an F320S so I can neither flash D802 kdz/tot nor get SU in adb shell.

Long story:
I tried to install Cloudyg2 version 3 without noticing, that it was for the korean model F320S.

I managed to wipe everything, ended in fastboot mode, loaded aboot etc. and was able to get to download mode.

The problem is, the phone identifies as F320S, so I haven't been able to use LG Flashtool to install a D802 tot or kdz-file.
LG Flash Tool 2014 and lgflash with "Automatic Offline Procedure-vbs" both stop at 2%.

So does the straight up LG Mobile Support upgrade recovery.

LG Flash 1.8 (for .tot files) gives the following error message:

BIN: BIN_LGD802AT-00-V10b-SEA-XX-SEP-04 (the rest is outside the window)
SWW: LGF320SAT-00-V21r-SKT-KR-APR-09- (the rest is outside the window)
SWOV: LGF320SAT-00-V21r-SKT-KR-APR-09- (the rest is outside the window)
Device Model is different!
Check Phone or DLL

I have tried with several versions of the LGUP8974.dll with LG Flash 1.8 without even getting that far. I can only get this far with LGD802_20130912_LGFLASHv160.dll.

So I've tried flashing F320S kdz-files, which I can. I've tried the following:

KoreanSKT F320S F320S11G_00.kdz (which is Jellybean)
Korea SKT KitKat F320S21R_00.kdz (which is Kitkat) and
F320S28D_00.kdz (which is Lollypop)

All of them sticks me in a boot-loop.

All three gives me access to download-mode, but I kan only change between F320S roms.

The Kitkat version gives me access to an ADB-mode by turning the phone off, then holding power and vol+ for about ten seconds. It gives me ADB-access, but the screen is black with the backlight on. In that mode, I've tried Ioroot, Vroot and Kingo root. Ioroot and Vroot doesn't work, but Kingo does to a degree.

I can also reboot into recovery and sideload either kk_root.zip or datroot.zip.

All three options make the phone show up as rooted in download-mode. The problem is, it doesn't give me superuser (su) when I use adb shell.

I've tried sideloading both Chainfire and Koush superuser-zip-files, but both fails with these error messages:

Chainfire's supersu:
E:Error in /tmp/upload.zip
(Status 255)
Installation aborted.

Koush superuser:
E:footer is wrong
E:signature verification failed
Installation aborted

As far as I can tell, there's three or four options:
Get su and install custom recovery
Get su and edit build.prop to D802 so I can flash a D802 kdz- or tot-file
Or find some flash-tool or .dll that lets me flash a D802 dkz- or tot-file

Maybe finding a way back to fastboot and using Linux to flash the right files to the right partitions.

Any help is appreciated! I've spent most of the week googling...