Well shit, this is wrong on so many levels..
First the RAM in the "wrong" slot, although I'm not sure what that would be in the case of a single stick. In my experience with old ddr3, it booted with a single stick in any slot, but I think that might have been the odd one out and not the norm.
Second, your GPU should work in the slot it was meant to work in, which on your mobo is closest to the CPU with the extra shielding on it! If it doesn't, then it's highly likely your mobo is bad! I have checked exactly your mobos manual, it could be perfectly fine to run the GPU through that, but it's a new mobo! It should work!
Then there is the SSD /sata issue. It should boot! Maybe not work, not start windows, but it must show something on the screen and boot!
So, at this point, I'd highly recommend trying one more thing: try to get it up and running with two sticks of ram in proper dual channel mode (this is when slot positions matter). Try both pair of slots, even if it happens to work your first try! You do Not want to be stuck with a mobo that has a broke ram slot.
If it dies again, try the other ram stick only, see if that boots fine . If that works, it's definitely a mobo issue and you should send it back under warranty ASAP!
This should also help figuring out if the ram is bad.
Believe me, I know how hard it is to let it go, even if it only works in a certain messy way, but in the long run, it will be worth that extra time to have an actually reliable system!
Tldr.: mobos borked, ram might be too, let it go, warranty exchange recommended to avoid future pain!
Extra thoughts: so many weird issues. Dodgy booting, ram positions, sata not working, GPU slots... all this could be nothing more but a badly seated CPU! Or even if a small speck of dust or something is underneath the Cpu! I've seen weird shit like that, although not recently.
How about instead of hours of messing about with dodgy windows installs and ram slots, you take off that cooler, release the CPU clamp carefully, slightly pick up and place down the Cpu again, and clamp it down again? If you are feeling adventurous you may take out the Cpu fully and check visually to see if all the pins still look fine on the mobo, but you might need a magnifying glass for that.
In any case, it may be worth a try!
