I have never run an airboat on snow, you can figure that out from my signature. But in my opinion, the issue you are having is a function of a hull shaped like a wedge, narrow up front, when you want the wide end up front. Triumph tried to sell that as the shape of things to come, but they were wrong.
Add in a weight center up forward and the problem exaggerates. A wide nose with narrower rear makes the whole thing track well. As it is, you hit the gas and your hull wants to dig and roll, Port or Stbd. It has to be squirrely on the rudder.
Just look at the shapes of snow ski's these days, fatter up front and you turn by putting your weight forward. Same thing is happening here, except it is skinnier up front, even worse. In the old days, snow skis were pretty straight and you turned by putting your weight on the rear and praying you didn't bust a@@ backwards. You are beyond old school here.
#1, pitch the prop to blow up at the rear, you need all that you can get there. Worst case it will have trouble planning and porpoise at speed on water, not a key issue right now. Keep pitching it up until things improve or it won't move!
#2, You may end up needing runners to make this hull handle decent. Unfortunately, that is going to kill much of the advantage of having an airboat. Try some 1/2" UHMW (Poly) strips on top of the poly you already have. Try 3x, 1 center and 1 each just on the nose edges and straight back.
#3, you have all winter to play with different shapes of UHMW before you build hull #2. Try some ski's outboard up front...
#4, your a smart a&&, fix it with software, that stuff weighs nothing.
That said, hit the water first/now if you can, just to have that experience before it's frozen solid up there and we are thanking God for the nice comfortable weather. #5, I'm not Cuban, but I do normally fail the Wet foot/Dry foot test.