Hebrews 2:14 Since therefore the children share in flesh and blood, he himself likewise partook of the same things, that through death he might destroy the one who has the power of death, that is, the devil, 15 and deliver all those who through fear of death were subject to lifelong slavery...17 Therefore he had to be made like his brothers in every respect, so that he might become a merciful and faithful high priest in the service of God, to make propitiation for the sins of the people. 18 For because he himself has suffered when tempted, he is able to help those who are being tempted.
Notice in this section the cause / effect statements:
2:14 Since... he himself partook...
2:17 Therefore he had to...
2:18 For because... he is able..
Christ's incarnation was not a fancy or a lark. Christ did not come as a man because he wanted to know what being a man was like. The incarnation was the only way to redeem mankind.
Verse 14 says that man is flesh and blood, so he became flesh and blood. Let me put it a different way. Man is subject to death and greatly limited, so he became subject to death and greatly limited. Philippians 2:7 says "but emptied himself, by taking the form of a servant, being born in the likeness of men." He emptied himself. He set part of himself aside and was formed as a servant.
So how much humanity did he have? So how much deity did he have? Hebrews 2:7 says "Therefore he had to be made like his brothers in every respect." Gregory of Nazianzus stated "That which is unassumed is unhealed," in his argument against the ancient Apollinarian heresy. Romans declares that Jesus is the second Adam.
Luke Stamps, assistant professor of Christian Studies at California Baptist University, wrote, "... Christ is in possession of an unfallen human nature, but during his state of humiliation he lived and moved and had his being in a fallen world. So even the incarnate God was not immune from the horrors of fallen existence. 'For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin" (Heb. 4:15).'"
Very God of Very God... like his brothers in every respect.