Uhhh,
I strongly recommend you remove the actual caliper during the procedure. This lets you clean carefully around the pistons and reduces the likelyhood of damaging a pad while putting it in place OR while pushing the pistons back in (side note it's a good idea to clean the pistons prior to pushing them in so you don't damage the seals.
Also I noticed you used the screwdriver to only press against PART of the piston, and you levered it against the disc. Both are bad ideas, you could cock the piston in the chamber and get it stuck in place, and you could warp the disc.
Finally, I'd suggest apply a SMALL, SMALL amount of assembly lube to the pin portion of the pad retainer (just a light gloss coat) as it can help prevent wear on the pin over time.
All in all, I would not use this method to change my or anyone's brake pads. Sorry tdiv.