On non-belief and the existence of God

[Neo-Scholastic]

Within the Christian framework, it is believed that God exists, and that there are propositions p,q,r...z that are *necessary* for us to believe in order to be saved…

Only among certain mainline Protestants (like Lutherans, Presbyterians, and Baptists) that preach “faith alone” hold this position. The Roman Catholics allow those outside the Church to be saved if they have “perfect contrition.” It is also not a problem for New Church, Unitarian Universalists, Quakers and other heterodox groups. I don’t think Methodists have a very clear teaching on this, and I grew-up in a half-Methodist church community. These same Christological and sorietological debates have gone on since the first century.

...this is something that can very easily be avoided by God himself if only he would undeniably reveal himself as the God of Christianity. He has the power to do so, and the will to act by.

I don’t think so. Even if YHVH was printed on the blood cells of every human being, it still would not be undeniable enough for a staunch naturalist. That stamp could be the maker’s mark of ancient aliens, right?

… we actually have very clear examples of people who directly witnessed God in His almighty presence and yet, freely chose to rebel…Adam & Eve… Lucifer and the fallen angels…

Very true. Anyone can see that simply knowing the truth is not sufficient without the will to act on it. Most people know that a high fat simple sugar diet is bad for you, yet many still continue to eat unhealthily.
Those who know the truth but lack the will to act on it, no matter how well informed, cannot even follow the dictates of their own convictions. Those who truly desire to do the right thing will do so when they know the truth. These people can be instructed by the Lord. Your examples (the original parents and the devil) also make good proof-texts for why the ‘faith alone’ doctrine is not the best one. Orthopraxy trumps orthodoxy every time.