@top_driver
Last ditch desperation measure: if your mobo has an onboard graphics chip you might be able to try removing the graphics card from its slot and booting only as far as the BIOS screens.
This is a catch-22, in my setup, as I need to be able to reach the desktop to be able to switch driver to the onboard chip.
For this, you need a cooperative bruv or local computer hoarder, to borrow a known-working gfx card to see if that's the source of the flicker.
Except Micro$oft don't allow for contingent component swapping and will decrement the hardware change counter. They're mean, that way.
Like I said: last ditch desperation measure.
Good luck, fixing it. Sleep helps, with decision-making, in these situations. I err on the side of obsessively trying to get the thing sorted out before I sleep, in case I forget where I've progressed to. The good thing about AB is that you've got notes to come back to.