Thanks, guys! By the time I saw the replies I already buttoned everything back up. My friend and I were pooped so we gave up on getting the rear rotors off and are gonna try again at some point this week. Fortunately, replacing the front rotors went perfectly smooth. ALL (front + rear) guide/slide (w/e) pins are cleaned and re-lubricated, all caliper brackets were cleaned and the seats were lubricated, and I cleaned the backside of each pad and added a bit of lube there. The drive home from my friend's house is about 14mi, and it was a good drive. There's no more steering wheel jitter, no more of that annoying "whoo...whoo...whoo" noise, no more squeaking without application of the brake (albeit it was raining when I drove home, interested to see if they'll squeak when it's warm and dry outside; i should be ok though), etc etc. pedal feels good... and yeah! Everything is good. Gotta get those rear rotors off though. Ugh.
And I've gotta replace those "bracket shims". I didn't bother putting them back on because I didn't have a clue where they went lol. Didn't take the bracket off the other side so no worries there. Yet. Lol. I have all the old hardware in a bag. Including those "shims" that fell out. I also figured that impact screwdriver would be crap. It has a rubber grip lol. Worked like a charm in the front, even though one of the rotor screws came out without the "impact" and instead just a bit of elbow grease and the screwdriver. Didn't take much to it, anyway. The screwdriver started to cave in on itself too, my friend ended up taking the whole thing apart and hammering it back into place (the metal part that you hit with a hammer started to literally cave into the grip, diminishing the tool's overall efficiency) and so it worked for about 5 more minutes........ and I can't get the bit that's in it.. out.. so I'm just gonna pretend I never bought that stupid thing lol. It has a 1/2" drive and a #3 phillips bit.. and I think that's the one that's stuck lmao
Nonetheless though I'm satisfied. A bit irked that we couldn't get the rear rotors off. But... another day.
Also, I think I'll need a smaller ratchet and smaller torque wrench. I had quite le struggle working with my torque wrench in the rear, and mostly with the upper bracket bolt lol