The differences result because Creationism begins with the Book of Genesis, an essentially religious approach, and Intelligent Design considers the hypotheses that either the world was created by an intelligent designer or it was not, and considers the weight of evidence on both sides.
By the way, I don't think Creationism is scientific in any way, manner, or form, but I have some sympathy for it. It was an attempt to get religion back into our schools through the back door because our tyrannical courts decided that the freedom of religion clause in the Constitution is meaningless. If it were allowed to teach about religion in school, then it would not be necessary to pretend that Creationism is a science.
No it doesn't. Once again you're imparting more substance to ID than it actually ventures to claim.
ID'ers have often noted that the "intelligent" agent could itself be a creaturely being. ID only "infers" the presence of "intelligent design" here and there, in this or that case. Such "design" might easily, in various scenarios, be present in a world that was not, overall, a product of creation.
Face it: philosophically ID is contemptably timid. A real creationist should be ashamed to defend it.