Not sure if brake fluid would eat teflon tape, but those are compression fittings. Compress them with appropriate torque (We allways used the ‘goodentight’ standard), and if they leak a drip, compress them some more...
I know taking them off I had to use a bit of force. Just a slow, steady force where there was no jerking around or anything. Glad they came off clean.
Also, putting the old brake pads in the new calipers and putting them in position on the rotor, I had about 1/8th in clearance. Sound about right?
And the pistons are all the way down in these calipers, not extended at all.