As a Christian, I wonder how much the questions produce skewed responses.
I don't think the federal government should advocate Christian values but should promote those values expressed in the Declaration of Independence and Constitution. Those values include that all humans are "created" equal (by God) and endowed with unalienable human rights.
Keep in mind, the writers of these documents believed in God, but as Deists did not believe in "Christ" as God's son. Why is God important? Because it makes even government accountable to a higher authority and thus subject to the people rejecting government if it fails to protect "human rights and civil rights". It is one reason that communism embraces atheism, doing so eliminates a higher authority.
Under the Constitution, people have a right to "exercise" their religion in public including public places. What we don't want is one religion being given preference over others.
So, public schools are not a place to "restrict religious expression" but a place that allows everyone to express their beliefs in a manner that does not interfere with others. As a Christian, I would not be offended by Muslim students praying as their religion dictates or a Jewish student wearing a kippah/yamaka to class. Let's not discourage religious expression but encourage it.
We are not an "atheist" nation, but a nation that celebrates religion without embracing any "church" or denomination or particular faith. I absolutely support the separation of "church" and state. Church does not mean religion in general, but rather government should not embrace a state "religion" like European nations did. Someone who declares there is no God is making an assertion that only God could make. Let's avoid all "particular" religions and let them compete for the hearts of people.
Absolutely, our government should not advocate a specific set of beliefs.
The success of the United States is part of God's plan is a trick question. Whether the US is successful, fails, or any other outcome will conform to God's plan. Everything in the universe conforms to God's plan. The second part of the trick question is "what is God's plan". Some believe God's plan is to just let the universe run like a clock till it runs out. Other perceive God taking an active role, which means if God's does nothing the universe "conforms to God's plan."
As a nation we should encourage people to respect the religious beliefs of others rather than try to suppress their public expression and exercise. Radical atheists and Christian Nationalists suffer from the same problem, attempting to impose their beliefs on others. Sadly, both groups are oblivious that they are both guilty of the same "sin".