Nick insists it is orthodox to say when Jesus slept that “God was asleep” because Jesus is the second person of the Trinity.
Here, Nick appears to part ways with folks like Ambrose.
Ambrose - Exposition of the Christian Faith - Book II, Chapter VII:
56. As being man, therefore, He doubts; as man He is amazed. Neither His power nor His Godhead is amazed, but His soul; He is amazed by consequence of having taken human infirmity upon Him. Seeing, then, that He took upon Himself a soul He also took the affections of a soul, for God could not have been distressed or have died in respect of His being God. Finally, He cried: “My God, My God, why hast Thou forsaken Me?” As being man, therefore, He speaks, bearing with Him my terrors, for when we are in the midst of dangers we think ourself abandoned by God. As man, therefore, He is distressed, as man He weeps, as man He is crucified.When Nick asks, “Can the statement ‘God died on the cross’ be understood in a truly orthodox sense?” the answer seems to be “No.”
57. For so hath the Apostle Paul likewise said: “Because they have crucified the flesh of Christ.” And again the Apostle Peter saith: “Christ having suffered according to the flesh.” It was the flesh, therefore, that suffered; the Godhead above secure from death; to suffering His body yielded, after the law of human nature; can the Godhead die, then, if the soul cannot? “Fear not them,” said our Lord, “which can kill the body, but cannot kill the soul.” If the soul, then, cannot be killed, how can the Godhead?
58. When we read, then, that the Lord of glory was crucified, let us not suppose that He was crucified as in His glory. It is because He Who is God is also man, God by virtue of His Divinity, and by taking upon Him of the flesh, the man Christ Jesus, that the Lord of glory is said to have been crucified; for, possessing both natures, that is, the human and the divine, He endured the Passion in His humanity, in order that without distinction He Who suffered should be called both Lord of glory and Son of man, even as it is written: “Who descended from heaven.”
The expression "in an orthodox sense" invites trouble, since "God does not exist" could be understood in an orthodox sense if further qualified, such as by "in the thoughts of a fool."
Standing alone, the comment that “God died” is facially heterodox, although it can be qualified to some other meaning. The Orthodox way to describe it is "Jesus Christ died on the cross." The church fathers agree.
Thus, Leo the Great, in Sermon 68, explained:
The last discourse, dearly-beloved, of which we desire now to give the promised portion, had reached that point in the argument where we were speaking of that cry which the crucified Lord uttered to the Father: we bade the simple and unthinking hearer not take the words "My God, &c.," in a sense as if, when Jesus was fixed upon the wood of the cross, the Omnipotence of the Father's Deity had gone away from Him; seeing that God's and Man's Nature were so completely joined in Him that the union could not be destroyed by punishment nor by death. For while each substance retained its own properties, God neither held aloof from the suffering of His body nor was made passible by the flesh, because the Godhead which was in the Sufferer did not actually suffer. And hence, in accordance with the Nature of the Word made Man, He Who was made in the midst of all is the same as He through Whom all things were made. He Who is arrested by the hands of wicked men is the same as He Who is bound by no limits. He Who is pierced with nails is the same as He Whom no wound can affect. Finally, He Who underwent death is the same as He Who never ceased to be eternal, so that both facts are established by indubitable signs, namely, the truth of the humiliation in Christ and the truth of the majesty; because Divine power joined itself to human frailty to this end, that God, while making what was ours His, might at the same time make what was His ours.Theodoret, in Letter 170, goes a bit further:
For in these very Chapters the author of the noxious productions teaches that the Godhead of the only begotten Son suffered, instead of the manhood which He assumed for the sake of our salvation, the indwelling Godhead manifestly appropriating the sufferings as of Its own body, though suffering nothing in Its own nature; and further that there is made one nature of both Godhead and manhood,— for so he explains "The Word was made flesh," as though the Godhead had undergone some change, and been turned into flesh.
And, further, he anathematizes those who make a distinction between the terms used by apostles and evangelists about the Lord Christ, referring those of humiliation to the manhood, and those of divine glory to the Godhead, of the Lord Christ. It is with these views that Arians and Eunomians, attributing the terms of humiliation to the Godhead, have not shrunk from declaring God the Word to be made and created, of another substance, and unlike the Father.
What blasphemy follows on these statements it is not difficult to perceive. There is introduced a confusion of the natures, and to God the Word are applied the words "My God, my God, why have you forsaken me;" and "Father, if it be possible let this cup pass from me," the hunger, the thirst, and the strengthening by an angel; His saying "Now is my soul troubled," and "my soul is exceeding sorrowful, even unto death," and all similar passages belonging to the manhood of the Christ.