Back brakes install

I replaced all 4 brakes on the vehicle roughly 2 years ago (at most, probably more in the 1 1/2 year range) and things worked great. The car doesn't get driven on a regular basis and when COVID hit, it sat in the driveway for nearly 3 months. Maybe driven 4 times in that time frame.

Not sure if that has any factor in things other than they were pretty rusty and I've done some clean up. But while doing this I've discovered something I think is "off."

Now, I hadn't replaced brakes by myself before, at least back brakes so that may come into play here. The fronts look and feel great. Those are fairly easy.

But with backs you have to deal with the ABS and/or e-brake and I think that's where things are again "off." I know in the backs you have that plug to remove and then you have to painfully use a screw driver and twist that lever in there.

1) What exactly does that lever do? I know it loosens, but what exactly does it?
2) Is there an easier way to spin that damned thing?

I say all this because the brakes are still pretty dang new. Tons of surface and material left on the rotors and the pads look barely worn, so that cannot be it. However, the e-brake when you pull it, you nearly can pull it all the way up before it engages. It works, but I know when you pull it that high that typically says the brakes are shot, which they are not. Leading me to believe something was missed in the install.

Just looking to confirm or debunk my theory and hear any thoughts and suggestions you may have.

Thank you.

-Allen (you've probably gotten to know me pretty well, I've posted quite a bit!)