The white smoke is burning coolant n gas. I have a feeling either a head gasket, intake gasket or both. Have you checked the oil and the coolant levels ? Check your fluid levels and what they look like . Milky oil is water/ coolant in oil, white smoke = burning coolant. You have either a head gasket leaking or intake leaking and going out the tail pipe. That will foul plugs and cause a miss this case it sounds like the engine is shutting down the affected cylinders 1 & 6 ....maybe a cracked head too. Check the plugs wet plug =water in cylinder= cracked head check w a light to see on #1 if not bump the engine if it blows coolant w the plug out ....cracked head . Saw this before on a 5.9 360 Ram 2500 at work . The heads were shot and cracked ....literally a cooked motor. However it doesn't explain it only happening in Reverse. Those senarios are constant engine not transmission