As you will have noticed, Celia, formatting doesn't work in the question field. That's because it was designed for much shorter questions. We don't mind at all if you split up your thoughts into separate questions, and it might also help you organise your thoughts. For now, I'll just follow along and answer what I see.
- Do you realise that with each exchange we're looking further back in time? You meet each of my responses with, "But how did X get there in the first place?" Eventually we'll reach the stage when I simply don't know, but beyond that is not simply a gap in which gods must sit, as you'll see.
The Earth formed from a cloud of loose rocks and gases, containing nearly every known element, which was pulled together by gravity. The heaviest elements, like iron and lead, sank towards the middle. The lightest elements, like hydrogen, nitrogen and oxygen, stayed around the edges. The heavy clump in the middle solidified and formed the rocks which make up the planet beneath us. The aura of gases around it became the atmosphere. Some of the hydrogen and oxygen combined to form water, and rained down into what's now the oceans. The earth, air and water were now separate.
- They were not stable, though; earthquakes, mudslides, lava flows, winds, tides and rains still moved everything around, slowly and quickly. That's how the molecules of everything came together, and still come together every moment of every day.
- The likely reason that life isn't still forming from scratch is that the combinations were different back then. For example there was a lot more ammonia and methane in the air; what if those two are needed as gases? (This is very likely. In an old experiment, they shot canned lightning into a replica of the ancient atmosphere. They produced 22 amino acids.)
- Most chemical reactions occur as a result of contact and friction between atoms and molecules. That doesn't mean that all contact causes reactions, but with more and varied contact you will likely get more types of reactions. In a muddy, gassy swamp, where the earth, air and water all mix together, you've got massive potential for interesting new combinations.
- I'm not a good enough chemist to explain the origin of self-replicators. This short video shows one likely way.
- The Big Bang was when everything in the universe rapidly expanded outwards from a single point. It's often seen as the beginning of the universe, but it ain't necessarily so. The vast amount of material in that single point might have always existed, and spent some time compressing together beforehand. It might have been contributed by another universe, one of many. Or, if you subscribe to a certain part of quantum theory, it might have emerged spontaneously from a quantum "foam".
- If you use a god to explain the origin of the matter in the universe, you then need to address the origin of the god. If you declare, without evidence, that the god has existed forever, then why not declare that the universe has existed forever and didn't need to be created? As an explanatory device, gods are quite useless here.
- Not every effect of evolution must be beneficial. A new feature doesn't have to be perfect to be passed on, simply more beneficial than the alternative when all's said and done. The benefits just have to outweigh the costs.
Think of all the "crap" emotions put us through and consider how many lives are actually lost. Just how many suicides are there, anyway? Compare this with the billions of little nice things people do for each other every day, just because it makes them feel good. Consider the children who would not exist without their parents' love and devotion to each other in the face of any circumstances. The benefits of emotions outweigh the costs for most people, most of the time. That's all it takes for them to be passed on.
- Nature, as Darwin said, is red in tooth and claw. Countless animals die in fear and pain because they have been defeated in pursuit or battle by other animals who intend to eat them. To me, this makes more sense if there is no god than if a god continuously allows all this suffering. (The Christian response to this is that even the most loving animals don't have souls, and although we should be nice to them they are not ultimately important.)
- Life does just go away. This life will end for each of us. Does that make it any less enjoyable to live? Doesn't the possibility that there is no afterlife make this life all the more important? Think of the things you enjoy in life. Would you enjoy them any more or less if God has never existed all along? Why does life need to have meaning to some distant, external observer anyway? If it has meaning to you, if there is something you have to live for, that's plenty. Atheism does not lead inexorably to nihilism, as Christians sometimes charge.
- Humans think there is "something more" because there always is something more. The universe, and even the planet, has more in it than we can ever explore in one lifetime. Simply because we can, we extend this beyond the natural world and wonder about the possible existence of the supernatural. It's at this point that we may not have any grounds to continue. I think it occupies our thoughts anyway because there's no good way to explore the supernatural. It's a permanent "undiscovered country".
- You've developed a great many questions about your own faith. There are many answers the faithful and those without faith can give you, but there are no concrete answers and there may never be. The nice thing is, you don't have to be sure to be happy. I'm not sure there are no gods, but I think the chances are so low that I am content to live my life as if there aren't any. It's like going out at night despite the tiny possibility that I'll be hit by a meteorite; why bother to worry about it?