BNA is my home airport, so I can help a little.

Maximum time between farthest WN gates is 5 minutes at a brisk walk.

Like anywhere else flights can be late, but I usually arrive on time or a few minutes early traveling into BNA. Weather can affect that and often does particularly in March. March is the beginning of tornado/severe thunderstorm season here.

If you are close, they will hold a flight for a few minutes, but it seems to be more common late in the day.

If your flight falls behind by a posted 15 minutes or more, they should move you to the earlier flight if there are seats.

You can enter the flight number here to see the recent history and also the complete schedule of the of the flight number for past flights. Flight numbers change all of the time, so it may not show up. (Tried it, did not work. 439 out of RDU? California number and may be a new number.)

MSY to BNA is 1.5 hours approx. Grab the first middle and sit close to the front. It is not too bad for 1.5 hours. It can make a difference of 5 minutes or so.

104/439 is the only BNA connection I find for MSY-EWR and it is Sunday 3/10 only next week. 439 originates in MCO and comes from RDU to BNA. It is the last flight of the day to EWR out of BNA.