I agree, the GPT is the bit that worries me. I had a once I fixed with a corrupt system partition and broken keys in prodinfo before, so not quite the same. What I did to get it to a “known good” state was to actually work to backrev the code to 6.1 then, once the partitions were stable, upgrade it back to the version it was at before. I found that version by checking the blown fuse count. The backrev would have to be done with ChoiDujour(not ChoiDujourNX) unless you can get it to boot to something like atmosphere(In which case you could use ChoiDujourNX). The important parts are the PC version ChoiDuJour only supports up to 6.1, don’t use anything newer… You’d need the firmware package as a .zip and I don’t think sharing/hosting those is legal. You’d also need the exact non-system specific keys for 6.1 with no extra keys. Those keys are also legal to share/host. I can say this, the exact key’s you’d need the values for downgrading to 6.1 are these and only these:
You can find a guide on PC based downgrading at switch.homebrew.guide.
Finally I’d also recommend the Support section on the Team AtlasNX discord. They were really cool helping me learn/troubleshoot as long as you read and follow the rules.