Yes, but if God isn't existence, and everything a part of God, then from what do you think he created everything? I'm of the mind that He creates from within Himself
I think what we have confused here is Creation and Existence. Sure if God exists, then He must be part of Existence. It seems however, that the Texts imply that God isn't a part of Creation, but separate from it. Or.......they at least don't commit to either pantheism, panentheism, pandeism, etc. The Christian Texts merely describe the reality without committing to any forced definition. There is no prescription. You may commit to one view if you like, but it's just that your view may not be in good agreement with the spirit/gist or projected meaning of the description given to us in the Texts.
Creation being "functionally separate" from God doesn't mean that we can't be "in" God, or God in us, but us being in God and God being in us doesn't mean that we are not distinct from God. The relationship cannot be compared to normal physics. By "functionally separate" I mean that the functionality, properties, nature, personality, identity and behaviour of God is distinct from the identity and functionality of Creation. They can connect with, mingle with and penetrate each other, even to the extent of overlapping and occupying the same time and space, but they are distinct in identity and functionality. It's not "normal physics." Actually, regarding what I said before, there is no physics, or at least I won't commit to any physics. This is just a description.
and you know . . . Christianity is driven by descriptions, not prescriptions. The New Testament describes, it doesn't prescribe.
"Us in God" and "God in us" don't mean the same thing. They could both mean that one is making itself a home or place/purpose for the other, but not necessarily a home/place/purpose in the same manner. "Us in God" means that God makes Himself a home in the sense that He provides the environment for us. He makes Himself into a world/environment/universe for us. It is like Him becoming a bubble of living space in which we live. We, in return, dedicate our lives to doing things that honour Him. This bubble of living space (God's world) is like a temple or spiritual house in which our daily work is a sequence of rituals that we perform for Him, not in the sense of ceremony, but in the sense of fellowship with God and other human beings. We are, actually, that bubble of living space, that spiritual house in which we work for God. Both us, and God form that bubble.
"God in us" is where God penetrates our soul and gives us the energy, inspiration, motivation and personality to be able to do the things we do in the Bubble in which we live. It's like a mutual soul-to-soul penetration between God and Creation.
The Bubble which is our living space is filled by God's Spirit, and those in that Bubble are part of the Fellowship of the Spirit. The Spirit which fills the Bubble is the air we breathe, so for those who live in God's world, the air they breathe is the
Spiritos, the breath of God. This is the "us in God." The Spirit not only fills the environment/world in which God's people live, but fills the heart and minds of the people in the Bubble. This is the "God in us."
This configuration at present doesn't exist, at least not in a time and place in which we can all experience it. I would say it's destined to happen in the Age to come.....