ExBethelite....you have lots of big questions, just a reminder to be patient with yourself in pursuit of answers. I also immediately leapt to the ultimate questions of 'how did it all begin', when what I should have asked is; have I really investigated manageable topics like Bible history and science or have I accepted the conclusions handed me? Unconsciously we leap to the unanswerable questions as a way to avoid dealing with questions we can answer.
Currently on this forum there are a couple of basic threads on these type of topics. Take some time and take small bites. If you have questions dig a little deeper. Ask questions, there are people here of all stripes so you get a variety of perspectives.
What I'm suggesting, is only that what you have believed to be true of everyone in other denominations, might just be true of yourself. They have been told they have the "truth" and have been told that the proof is inescapable. They have a community that shares those beliefs and that acts like a family in many respects.
Why are people confident the Catholic church is the "true" faith? They have preached the Gospel for 1800 years or so all over the world, sent missionaries who risked everything to" save" the indigenous people They are the reason billions of people are Christians. They claim to have an unbroken lineage right to the Apostles of the Gospel.
Why do Baptists believe they are the "true" faith. They use the Bible extensively and have experienced powerful proof of Holy Spirit. They send missionaries all over the world.
Why do Mormons believe they have the "true" faith? They have an international brotherhood preaching around the world, are persecuted, high 'moral standards' and a recent revelation from God.
Why do 7th Day Adventists believe they are the "true" faith? As a sister denomination to the International Bible students they, after all, share much of the WT theology and have been sending missionaries into the world for longer than JWs. When I was deep in the Amazon striking out to preach where no one had before, we found a small 7th Day Adventist church already there, as well as a tiny village with church established a hundred years earlier by Anglican missionaries.