You do a good job of keeping emotions to a minimum here, it gives you more credibility… very nice. I just wanted to shoot a quick comment for you/others to consider:
all existence – current knowledge = spirituality
I would argue: The “spiritual” is just as scientific as physics… in fact it is part of physics. Just because at the moment we aren’t capable of seeing it that way doesn’t mean it isn’t so.
Consider sound: Sounds were considered completely independent from physical forces until the discovery air particle movement in wave form.
Consider prayer: Although I don’t know the statitics on successful praying it seems logical to attribute those successes to mental ability changing the environment rather to God’s ear. We aren’t aware of the forces our minds are capable of at this point… at least not in a measurable/scientific way. Although that might seem a stretch for lots of people…. theistic attribution is just a bit more of one.
The universe is science… spirituality is science…. God is a label for the yet to be understood…. because we will never know everything the label will always be there… “God” will never die.
I agree that, in an explanatory sense, “God” is often used as a synonym for “I don’t know.” Even so, I wouldn’t go as far as you do with the concept since there is a great deal we don’t know that could meaningfully be classified as spiritual, and very little classified as spiritual that’s really as mysterious as some people believe.
I do think you can get a “spiritual-type” feeling from the wonder of the world all around us, though, and I encourage such feelings.