your not supposed to teflon tape them in, nothing on the threads at all, the rubber Oring does the sealing. that thing is never gonna come out now, your gonna spin the fitting off the wall and then your in deep doodoo
gonna have to drill the middle and cut it out using surgery VERY CAREFULLY. this isnt an easy DIY see if you can find a video or something to guide you along. once you get a good notch on it its plastic it should implode itself and come out.
You could take a chance on messing up the edge of the return fitting and holding onto it if theres enough bite with channel locks and then try loosening it, need to hold back on it somehow or cut it out.
sorry for the bad news