I think that you have a major problem. My hunch is that your reverse is not fully disengaged. So effectively you are driving around with reverse on all the time. Something is really wrong for the transmission to get so hot. You should be able to touch the transmission after driving around. Only the torque converter gets so hot you can not touch.

Put the rear wheels up in the air and put the shifter in neutral and see if the wheels are turning forcefully.