My tj heat will slap run me out of that thing
I would confirm someone else's temperature coming out of their vents before you tear it all apart. 140* degree air coming out seems decent to me. Even though your engine coolant is 200* the air coming out isn't going to be that hot. I could be wrong though, just like most meteorologists.
Mine gets so hot I can’t comfortably place my hand on the center dash vent if I have it on the hottest setting for long and it will absolutely make your feet sweat like a pig if you run it for long on the bottom vent.