I've read your post, plus the comments below.
I find it difficult to adjust my thinking to your description of why the universe exists. The universe, you say, does not exist without us, but then, how do we come to exist? Surely the universe would first have to create us?
My belief, which has either influenced my writing, or my writing has influenced my beliefs, I'm not certain, is that we cannot have an effect on matter in our reality; not any that are strong enough to have consequence.
However, as per Eastern beliefs also, I do think that those of us who are able to reach a certain dimesion, all thoughts there become matter. Picture an elephant standing next to you and it will be. It is how the characters of my story have become real and all I need is to find a way for me to go to them.
The question is, where do those realities exist? Could they exist within our mind? Imagination has to be potential in potential, so that would be a good place for alternate realities we create to exist. Such cannot exist if they are to wink out of existence within a hundred years or less, so it means our minds must be eternal - a part of our souls. After all, for souls to evolve, they must have minds.