OP is one of those people that worry about gpu "sag" so they put it in the lowest slot and introduced a foreign object to hold it.
picture shows nothing wrong other than said graphics card placement.
We dont know what games you like to play.
At what resolution you play at.
What will be other components in that system will be.
How much you would like to spend.
Without knowing those, 3090 is a better card however gains might be not worth the step up depending on your answers above.
It is a hard game to get into. It also has many flaws and recent flight of players shows that they arent doing enough to fix it. I can think of many other games I would rather play for 52euros than Tarkov.
Eh? Are you confusing surface temperature pain threshold? Other than that I have no clue what you mean. There is no normal as each device is different.
The way most laptops work, they require a what is called a mux switch in order for your displays to bypass iGPU. Your laptop is an entry level AMD laptop, so its safe to assume it doesnt have one. Your iGPU MUST be preset in order for you to get any display output from your device. If your performance is below what you think you are getting, make sure you selected the proper GPU in settings and both your gpu drivers are installed. There is NOTHING else you can do.
Disabling iGPU is a dumb thing to do. Install its drivers back as you need it.
I wouldnt even call this an idea. RDP doesnt work for gaming. Windows also doesnt do multi-users at same time very well (infact it wouldnt even allow two users at once, be it one rdp and one local user). VirtualBox doesnt offer any sort of 3d acceleration or VGPU solution, so that is also not even going to work.
None of those things you listed will work.
CPUs can die abnormally, I have had one die on me last year while watching youtube.
OP, your symptoms replicate how my 5800X died, so your CPU also might be dead too. However suggestion above is a good one, try that first.
I still feel like $300 is too much for one of these. However at this price I definitely would have gotten one just to experience how shit these are myself.