These were big questions for me too. I spent a lot of time in fundamentalist circles and was always bothered by the poor answers I got. It contributed greatly to my becoming agnostic for a few years.
I think you got some great answers before the thread was derailed. I don’t think I can do better, but I’d add that for me for me the key was the concept of free will. From an agnostic perspective we must have free will or the universe is absurd. So I had to start by accepting that it’s real. Christianity teaches it’s real and God has given it so we have the ability to freely choose him. But how can it exist if we’re purely material creatures? If that’s all we were then we’d just be the sum of physical reactions. So there has to be a component that can transcend the natural. The Church teaches we have rational souls created at conception. It’s part of who we are, but it’s not physical. It allows us to reflect and make free choices. As far as we know no other creatures on earth have this. There are some very smart animals, but none that can self reflect.
So the answer to #4 is it’s impossible to evolve a rational mind. Everything in the natural is constrained by natural reactions and has no mechanism to choose otherwise. You can evolve very smart animals. Mankind can build very good AI. But true choice has to transcend the natural. It must have supernatural origin. It could not have evolved.
I’d answer #3 that all previous life forms were stepping stones to get to us. Humans didn’t appear out of thin air. There was a long process of evolution. Why did God create this way when he could snap us and our world into existence immediately? Why did he create whole galaxies that were undreamed of until recently? I don’t know, but who am I to critique the Creator. There’s nothing here that’s inconsistent with Christianity though.
#2) What seems random to us isn’t necessarily random. We’re literally watching Creation unfold. Eternal creatures like Angels were made in an instant, but we’re playing out in linear time. Why do us differently? I hope to find out some day.
I don’t have firm beliefs about how original sin works. I’d like to hear what some others think about that myself.
You got some good reading recommendations already. I’d add John Haught to the list. He’s a Catholic theologian who’s written several books on the subject of science and religion.