Great questions! I’m so glad you’ve asked them here. I look forward to what others have to share!
As for (1): Christians say they have real experiences with Jesus; other adherents say they have real experiences with their God or gods; we can’t both be right.
First, Christianity actually offers a pretty unique theology about a relationship with God. The offer to know God personally, not only as our Lord and Savior, but as our friend, is remarkable.
Second, Christianity can explain diverse religious experience. The Bible teaches not only about an authentic relationship with the Triune God of love, but also about people who are worshipping other gods. This is one of the major themes of both the Old and New Testaments.
Third, on atheism or naturalism, a primary explanation for why we believe what we believe is because it is conducive to survival. The majority of the world’s population is religious. Therefore, to enhance his or her own survival, shouldn’t the atheist consider a religious worldview?
Fourth, if my own comprehensive experience of the world is that my friend Bob exists, what are any of us to do if other people deny meeting him? If you say to me, “I’ve never met Bob, but I have met Sally,” so what? There’s nothing wrong with me continuing to believe in Bob’s existence. Based on the experience of the world that I have access to, it is rational for me to continue to believe that Bob is real.
Fifth, we could ask, “If God exists, would you be interested in a personal relationship with God?” If the answer is yes, then you could explore with them the question of whether or not God exists. If the answer is no, then ask, “Wait, why not? If God is real and interested in a friendship with you, you aren’t interested?”