why must evolution and ID be totally separate? Why can evolution by DNA code changes, not be an engineered process?
It is a good question, if a bit naive. The short answer is, because the evidence is completely contrary to an intelligent designer. In short, the presence of derived characters which serve a different function from the ancestral characters but often not the most efficient design for that character. The question is, if one is intelligently directing evolution, why not do the most efficient design based on the building blocks available? No, the evidence overwhelmingly supports that it it is natural selection which does the directing, not God.
If you have the answer, you are a fool,
If you are a believer, I would be a bit careful with that one. See Matthew 5:22.