In the last fourteen years, I have flown to MCO ten times. Six were out of Fargo and four out of MSP. Those MSP trips were the first four out of five. When there were four of us traveling, it was cheaper at that time to drive to Mpls and stay at a park and fly hotel. When it is just me, by the time I pay for the hotel and gas, I have covered the added cost of the flight. Plus that drive home is a killer. Not so bad with multiple drivers, but once was enough driving it alone. (I live about an hour from Fargo.) I will cut back on other parts of the trip to fly from FAR.
I work at a school so many of my trips are over our October school break. Delta knows this

I think you might have better luck finding a good price in December especially if you aren't going right at Christmas time.
Are you flying Saturday to Saturday or are your days flexible? Right now I could only check a Wednesday to Tuesday on Delta. That was a great price. Saturday to Saturday could be more. And oddly enough for the flights I checked today - and I have sometimes seen this happen before - it was about the same flying out of Fargo as MSP. I know you can't count on that often, but I have seen it before. Especially at a time when MSP to MCO flights were way high.
So many things affect it - days of the week flying, time of day you are willing to fly, etc. Since I have done this for several years, I have usually watched flights a year ahead to get an idea of what I might have to pay. Then when the first days open to book, I watch daily. When it is at a price I am willing to pay for the days I want to fly and the times I want fly, I buy. Then try not to look again! There are times I was glad I bought when I did and others I wish I had waited. It fluctuates so much that it is difficult to tell anyone when is a good time.
Some say Tuesday through Thursday are good days to watch the airlines. But then I've had something good pop up late on a Saturday night and during my lunch at work. Flights can change within hours so if you see something you like - be ready. Keep checking - a lot! I wish I could give you some more concrete information. You're right. It's a crap-shoot!
I haven't done any research with United, American or Allegiant flights. I have considered flying through Chicago, but I'm most comfortable at MSP - and that area if I should happen to end up there overnight for some reason. I have family who have flown Allegiant and rented a car. They said by the time all of the extras were added on to their Allegiant flights, they probably could have flown Delta.
If you do connect at MSP - or anywhere for that matter - be sure to choose a flight with plenty of connection time. I've taken the Fargo-MSP-Memphis-MCO route two or three times because I missed my connection. This last time I had 1 hour 6 minutes between flights. The gates between the landing from FAR and departing from MSP are quite often/most always a distance apart. This time we landed a little late. I quickly made a bathroom stop, grabbed a sandwich to go and hurried to the next gate just in time to board.
Good luck!! What a fun trip to look forward to!!