When it comes to the existence of "God," I think 1 John 4:16 is the best and simplest answer:LOVE
"And we have known and believed the love that God hath to us. God is love; and he that dwelleth in love dwelleth in God, and God in him."
If this is so, then God is not some bearded guy in a white robe sitting on a throne somewhere; He -- It -- is a real but abstract force permeating all life on Earth (and beyond, if aliens are a real thing). "God" is not a person or a thing, but an experience that can only be understood through proper (loving) life.
Love never starts or ends with ourselves; we can't give love to another until we've felt it from another. But at the same time, love cannot exist in a vacuum, it cannot exist without life, and it cannot continue without being shared -- You can't store it away or save it; use it or lose it.
Maybe Shakespeare had it right:
My bounty is as boundless as the sea,
My love as deep. The more I give to thee,
The more I have, for both are infinite.
(Romeo and Juliet, II.ii)
Or perhaps it was John and Paul (not the Apostles; the Beatles) who got it right:
And in the end
The love you take
Is equal to the love you make...
("The End," Lennon/McCarthy)