You want to know about “proof that there is life beyond this world” and evidence of “the concept of an afterlife” and “spirit beings.” So let’s talk about that.
Here's a good starter for a conversation about the reality of the soul.
1. There is reason to believe we are more than just physical bodies because our thoughts and feelings don’t have any materiality. And if we admit that those exist but don’t have materiality, then we admit that non-material realities exist.
2. We have a sense of self that doesn’t particularly pertain to our physical bodies. Our sense of self (and our perception of self, not just in thought, but as an entity) gives evidence that we have a conception of an immaterial self. If we are aware of part of ourselves that isn’t physical, then we admit the possibility of non-material parts of us.
3. We have in our minds some idea about truth and falseness. Our perceptions of truth and falseness (which are necessary for scientific inquiry) betray a belief that among the random and chance happenings of evolution and naturalism, content (apart from natural phenomena that we can empirically experience) has arisen that we can trust to be reliably true. The reliability of cognitive content in addition to self-perception gives evidence that something besides pure materialism is present in our beings.
4. We can create a thought process that goes something like this:
a. Either you are a body and a soul, or you are just your body.
b. It is possible (by which I mean it is strongly conceivable, therefore I have good grounds to believe it is possible) for you to survive the death of your body (as evidenced by genuine "near death" experiences).
c. It is not possible for your body to survive the death of your body.
d. Therefore, you are not identical to your body.
The second part of your letter that I would like to comment on is that atheists “usually believe in the process of evolution.” This is correct. Since they are unconvinced about the existence of God, evolution is really the only other choice as to how things came to be. But, you should also know, about 35% of Christians believe in evolution, too. These Christians believe that evolution was the process God used to create.
Third, you mentioned Greg Stier’s observation about a lack of a ground for morality in atheists. I have talked to both camps, some of whom say that they have a morality based on a desire to survive, and that morality is a beneficial practice for the wellbeing of humanity. The others I have talked to agree that there is no such thing as morality, that life is completely meaningless, and raping a 5-yr-old girl is no different than getting a glass of water to drink. They are just physical actions. (Horrible.) Most atheists I have talked to are in the first camp: they believe in morality and moral action as contributing to the wellbeing and survival of the human species. So I would say Greg is giving a skewed picture of the reality.
We can talk more, as you wish.