“In the beginning was the word, and the word was With God and the word was God” John 1:1
"But of that day and hour knoweth no one, not even the angels of heaven,
neither the Son, but the Father only." Matt 24:36
It's really time to let go of the rope, since you've been tying yourself in knots for far too long (your Dawkins analogies etc. though amusing, only go further in revealing the total absurdity of Christian doctrine, especially when it tries to argue for a single, undivided necessary entity). I suppose it was Aquinas who really set this obfuscating affair going, whilst playing a totally meaningless game of intellectual table tennis. His principle philosophical/religious forbears, Avicenna and Maimonides, on whom his thought is parasitic, at least were able to focus their argument on a single uncaused entity. Aquinas comes along and totally muddies the waters with contradictory Christian apologetics. Contradictory, because the very scriptures on which he and other Christians attempt to assert the total divinity of Christ are themselves contradictory (see above for one more among many, some of which come from the same evangelist).
Where you seem to differ from Aquinas is in attempting to elide any sense of
distinct personages, but rather like to refer to modes of operation. This, I thought was the heresy of Sabellianism. (The weight of waffle is already weighing down my head - how do people continue with this twaddle for a lifetime?) Aquinas seems to have been at pains to keep the personages of the godhead distinct, and truly bemired himself: his only get-out clause seems to have been that "faith" would sort it all out for the believer.
However, I've no desire to get into an argument about the Trinity here: I wasted too much of my youth on such contradictory absurdities. Nor do I wish to continue the confusion by referring to the multitudinous interpretations of the atonement (though I think that Outrider, with his oblique reference to some kind of penal substitution idea I understand is not your bag, nor particularly Aquinas's). All these things simply serve to further confuse and undermine your 'contingency' argument.
You see, I puzzle why you bother. I've pointed out above that most who go to great lengths to prove a 'necessary being' or 'first cause' are anxious that this is the ultimate source of meaning and purpose for the world, and more particularly themselves. I said "What if it were evil?" If there were
nothing we could do to appease such a being, then it is a remarkably jejune exercise to try to argue for its existence. We are certainly better engaged in trying to find more about the vast mysteries of the world which we can actually investigate, and sometimes manage to find real proofs of the realities which we encounter.