Van Til was not a theonomist in the Bahnsen (American Reconstruction) sense of the word. This much is actually pretty clear. However, this is not to say that he was not a transformationalist.
"Is it not true that Christianity was meant to conquer the whole world for Christ? Yes it is. We have already said that we think of Christian theism, when we think of Christianity. That covers the whole earth. If we can successfully defend the fortress of Christian theism we have the whole world to ourselves. There is then no standing room left for the enemy. We wage offensive as well as defensive warfare. The two cannot be separated. But we need not leave the fort in order to wage offensive warfare."
Ref: Apologetics by CVT.
Reformed folks who claim to abide by Van Tillian presuppositionalism either clearly do not understand the dominion mindset that is a ***logical*** result of his apologetic, or they refuse to see it.