The beginning of the biblical worldview is that everything was created in harmonious order, but then everything was fractured by us and broken bits now cause almost all of what you mentioned. God did give us the appendix though, and we think we’ve figured out why a few years back, it seems to hold a backup of the intestinal bacterial that can restart it if it gets wiped out.

You don’t need to consider the hypothetical existence of God to be a true fact in order to be a good Christian.

Other than the fact that according to the Bible you need a personal relationship with God in order to be a Christian and spend eternity with God.

The main idea of Christianity is that earthly life is essentially an entrance exam for the next, true life. You live your life as best you can, then you’re judged afterwards, and if you pass - you go to heaven, which is supposedly a paradise free of evil.

See above, according to the Bible, no one will be judged good enough based on how they lived their life and the only hope of getting to heaven is a personal relationship with God, by which Jesus’s death in the cross can pay the outstanding debt owed from your life that you yourself cannot pay.