There is another recent thread in this forum in which the poster has moved from a DX camera to FX and is lamenting that he can no longer use his Tokina 11-16 wide angle. There's a recommendation for the Tokina.
But that post also shows the advantage of the DX format for wide angle shooting. I won't claim any DX wide angles will match the 14-24 for image quality, but there are some very good DX wide angles that are smaller, lighter, and less expensive than what you'd need to pay to move to FX. We tend to think of DX as giving more "reach" than FX, which can be an advantage at the long end. But I think people overlook the advantage of DX at the wide end where there are some nice lenses that are much more compact than what you'd have to carry to get the same angle of view on FX.
I'd certainly keep the 35-70 if I were in your position, and just add a wide angle to what you have.