Colpy, let me just first say I enjoy reading your posts tremendously. I find you to have clarity in politics and thought. You have the ability to condemn that which you admire when you see fit to do so. You and a few others are what keeps me on Canadian Content.
In reference to God in the Declaration of Independence (God is implied 4 times, but the word God I believe is what you are referring to):
When in the Course of human events it becomes necessary for one people to dissolve the political bands which have connected them with another and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.
The religious references in the Declaration are unmistakably deistic: it's clear that the references are not to the revealed God of Christianity.
In terms of the separation of church and state, be cautious when you try to interpret the US Constitution, it must be accompanied by texts that discover the intent of the founding fathers (as is normally the case with any Constitution)
Thomas Jefferson referring to the Establishment Clause of the First Amendment;
"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof . . . .", wrote a letter to the Danbury Baptists assuring them no religion will dominate in government, and he used the famous phrase previously uttered by the theologian Roger Williams, a wall of separation;
Believing with you that religion is a matter which lies solely between man and his God, that he owes account to none other for his faith or his worship, that the legislative powers of government reach actions only, and not opinions, I contemplate with sovereign reverence that act of the whole American people which declared that their legislature should “make no law respecting an establishment of religion, or prohibiting the free exercise thereof,” thus building a wall of separation between church and State. Adhering to this expression of the supreme will of the nation in behalf of the rights of conscience, I shall see with sincere satisfaction the progress of those sentiments which tend to restore to man all his natural rights, convinced he has no natural right in opposition to his social duties.