Uh, so, not content with the Spirit, you are arguing that the Son is also a contingent being?
Well, it really depends on what you mean by contingent. Because according to the some of the definitions of the word, the Son and the Spirit are not, but according to other definitions, they are. Look at how many different meanings Merriam Webster lists for the word:
1 : likely but not certain to happen : possible
2 : not logically necessary; especially : empirical
3 a : happening by chance or unforeseen causes b : subject to chance or unseen effects : unpredictable c : intended for use in circumstances not completely foreseen
4 : dependent on or conditioned by something else <payment is contingent on fulfillment of certain conditions>
5 : not necessitated : determined by free choice
So, I think you will need to specify exactly what you mean by that if anyone can rightly answer.
And how does the idea that the Father 'could have not poured Himself out into the Son', differ from the Arian position that at some point the Father willed the Son into existence?
It's really a different issue. In this view it still could be said that there was never a time when the Son was not, while the Arians assert that there was a time when the Son was not.
Because if the Father could have not, there must have been a point when He had not so that He could choose whether to do or not to do.
That's simply not true. There was never a time when the Father did not choose to beget the Son.