My answer? I am not theistic, but your answer that the Trinity is a “mystery beyond full comprehension” does not explain why Jesus prayed to God if they are both one.
Jesus was the Word made flesh. Why this was important was to demonstrate to his creation that God truly understood us, how we went about our lives. As any man would do Jesus prayed to God. Can we say he prayed to himself, perhaps, but to those of us who believe we know there is far more to it than that. My personal belief is that during Jesus Earthly ministry there was a "separation" of a kind, not complete but the man Jesus saw the world with Earthly eyes and lived a fully human experience while still maintaining heavenly connection with the whole.
Seems a tick confusing of course yet in the end its is amazing. And yes, from this the “mystery beyond full comprehension” DOES indeed answer the question, for we do not understand the HOW but we embrace the WHY.
God is powerful enough to be as he wishes, that he can both be with us as a man yet remain fully God is not hard to believe when one looks at the wonders he has made.
Why are you putting words in my mouth with a false quote? (I didn't say that...are you quoting somebody else...or was it just more convenient for you to create a straw man because you can't or won't more fully answer the Q?)
If you're not theistic, then what does all this matter to you re: how many gods there are? (Apparently, it doesn't)
If you're not theistic, then apparently it won't matter to you -- until you see Jesus face-to-face -- whether He is THE True God of the Universe -- or not. (THEN, it will be ALL that matters to you)
Because the human part of Him needed to.
That aside, define praying and explain why it's giving you such problems.