When re-installing the power supply, double check the position of the plug before inserting back into the chassis. Keep in mind that you need to hold the plug in that earlier (90 deg counter clockwise) position as you slot it in, otherwise you'll have a heck of a time twisting the plug back properly.
Thanks, Ben, for highlighting the little lip underneath the plastic tab! I was starting to get frustrated with the power supply!
My standoff screw was really tight and my T6 stripped the screw. :( But, because it's effectively just used as a post to stabilise the fan, I ended up using some surgical clamps, grabbing the standoff where the rubber grommet sits, and gently twisted the screw loose. No major damage because that part of the screw isn't really used! Just be careful and gently twist (patience is KEY) to loosen.
second the hint about the hair dryer!