In all cases, what is not known is covered and explained by a statement of faith that the theory is right.
There is nothing wrong with using a statement of faith to explain what cannot be proven. I do it all the time.
No.
First understand that ID is not a single theory. It is a class of hypotheses with the common features that the motivating force behind universal creation is not random but was created by the deliberate action of an intelligent life form.
ID is a hypothesis, not a proven conclusion. Furthermore, a proven form of ID would necessarily have data to indicate the specific nature of intelligence and method.
Those opposed to ID are closed minded, unscientific, and rule out a hypothesis without any basis for doing so, particularly since several constructs of ID fit all the data we have today. They reactionarily exclude ID as a hypothesis simply because it could be consistent with the Bible in some forms. That is atheistic thinking.
Scientific proponents of ID are not stating ID is the only possibility. (The labels in textbooks did not state that ID was a certainty either)
So ID is not a statement of faith because it does not presume the ID is a god, as required by most religious faiths. It is simply a possible set of solutions.
BTW: In science anytime we brainstorm a set of possible solutions to a problem we do not exclude any possible solution just because something similar may have beeen mentioned in the Bible. That would be unscientific and absolutely bigoted. It would also be stupid.