Well, I'm no expert in natural theology or Kantian philosophy but I think you got it backwards. I believe drstevej knows this stuff so maybe he can explain it. My understanding is that Kant believed God could not relate to man because he was too emminent. Van Til obviously did not state that. Natural theology, as an offshoot of Kantian philosophy, states that man reaches God through our reason, no divine revelation needed, in fact, divine revelation is impossible. General revelation, which is what I believe you were speaking about, does lead us to God but we still need divine intervention in our lives in order to reach God.
I did have lunch with Van Til a time or two. As WTS professor emeritus he spent hours on campus talking with students. Usually there was a crowd around him.
First, regarding Kantian Epistemology. That epistemology stated that man cannot know anything as it is because his senses distorted the data he was receiving. As for Van til he is saying that man cannot understand anything about God because man is unregenerate, hence the appeal to Christian presuppositions.
Regarding natural theology it was never believed to substitute for Divine Revelation via Scripture. Aquinas (natural theology) was defending knowledge that proved the existence of God, nothing more. In other words, the theology of nature (Ps.19), which proves that God exists. Aquinas never believed that natural theology could substitute for God's revelation via the Scripture (and being a Catholic, the Church)
Now, Til may be substituting his own definitions in place of the common usage of those terms.
Finally, Aquinas, not Kant is the defender of natural theology. Kant unhinged philosophy from any connection with objective reality and made it totally subjective.