Humanity is living in an (almost) endless painful cycle of civilisations rising, prospering and falling, like a phoenix rising from its ashes, only to burn again. No civilisation, nation, or idea can escape. Some might be able to avoid destruction for longer than others, but they will eventually meet their end.
Death is and should be inevitable, and it's a good thing. I have gotten over the fear of dying when I was eight, yet so many people, (way too many of them are adults) seem to treat death as a sensitive and even taboo topic.
I find the thought that I'll most likely be able to rest peacefully either in a state of non-existence or some sort of afterlife to be calming. I tend to think that the acknowledgment of our own mortality is the only thing that makes us truly enjoy life, as we know it won't last forever. This is the reason why people talking about technology that could make immortal people without thinking about the downsides enough really concerns me. Humans are supposed to be born, to live and to die.
If we want to define whether an action is immoral or moral, then as a rule of thumb, it is moral as long as it doesn't hurt anyone. (yes, this includes non-human animals) There are a lot of exceptions of course.
Humans are not superior to other animals. The reason I think that, in general, killing another human is worse than killing another animal is not that human lives matter more than lives of other animals, but instead that you shouldn't kill your own species.
About #3, do you view this as a hard rule? Not the animal part (vegan btw), the "hurting is always wrong" part. There are situation where I've caused harm to someone for the sake of others, their future, or a greater pleasure.
Also interested in the "not killing you own species" section of #4. I would also kill another animal rather than a human, but for other reasons. What do you think about hurting a member of your own species is uniquely bad?
It is not really a hard rule, I think there are a lot of situations where you have to hurt someone such as self-defense, having to eat other animals to survive and such. So it's like a soft rule of thumb, as there are a lot of situations where hurting someone is justified.
And concerning killing your own species versus other animals, I think we naturally tend to have more empathy for other people and especially the ones closer to us. Also killing a non-human animal outside of self-defense can be justified by needing food, but, well, eating another human seems to be worse than eating a cow.