Starting: Jacksonville, FL is where.
Soil: Sandy
Worry: RKN

Would you buy a dwarf fig and pot it or buy a non dwarf variety and plant it in the ground and take my chances? Or do you have a third option?

Why not buy a non-dwarf, and grow it in a pot, maybe even a half-wine-barrel, till it is too large for the pot, and then plant it in the ground. The extra size of the tree before planting might mitigate the effect of the RKN by giving the tree a head start. Just an idea.

I agree with pitangadiego, one more thing I would add, when you grow in the pot, don't lay the pot on the grass or baresoil. I would place it on concrete or a patio.

Consider planting some LSU varieties that are nematode resistance like LSU Purple, Tiger, Champage, O'Rourke etc. Jon's idea is a good one too.

Speaking with James Robin, he told me that the worst figs that were affected by nematodes were the LSU varieties. So not sure how resistant they are to RKN.

Should we plant the future planting area with French marigolds? I understand crop rotation, but this one sounds funny to me.

My sister's house is next to a dairy farm. The farmer sold the land and now no cows. The fig is for my niece. Her house is sevaral miles away. The other things in that area are tree farms. They grow a lot of tall pine trees. 
I'll have to see if they have the chemicals @ Ace Hardware on Blanding while we are there next week. Great tips!