In Hebrews 2:10 the sentence structure puts God (He) as the perfecter of Christ (the captain). It would be improper to suggest that Christ perfected himself.
Why is it, then, that the writer uses the phrase "for whom are all things and by whom are all things" as pertaining to God the creator, when the majority of scriptures using similar phraseology apply this to Christ? It seems a confusing way of ascribing deity to Christ.
Refs.: John 1:3,10; 1 Cor 8:6; Col 1:16; Heb1:2; also Gen 1; Mark 13:19; Rom 11:36; Eph 3:9; Heb 3:4; Rev 4:11.
The statement in Heb 2:10 is one of a number in the NT writings that unabashedly maintain the reality of the humanity of the historic Jesus, while also (typically in the same writing) equally emphasizing that he uniquely shares God's glory and is to be reverenced accordingly. So, for example, the thrust of Hebrews chapter 1 is on Jesus' full and unique divine status (e.g., 1:3, Jesus as the "effulgence of [divine] glory" and bearing or being the divine "imprint"). Then, in Hebrews 2, the author turns to make the complementary point that Jesus is also truly human, and so is able to function as the true high priest, intercessor, etc.
It's not one at the expense of the other for these NT authors.
The reference in the question to Heb. 1.2 is appropriate. The statement in 2.10 of Jesus being “perfected” does not come from a low Christology. Heb. 1.3 is possibly the highest statement of Christ’s deity in the New Testament. He is “the direct impression of that which is God’s true being.”
Hebrews also has a high sense of Christ’s humanity. That is the focus of this passage. One of the concerns of the letter is that the believers hold firm to their faith despite their sufferings and even grow from them. They can do this with Christ’s help because Christ shared fully in their physical life and became like them in every respect, except for sin (2.14, 17; 4.15). Indeed through death Christ provided atonement for their sins (2.17).
For this Christ was “made perfect through suffering” The term perfect means “complete.” Jesus’ being made perfect was not becoming complete in terms of no longer being sinful; it is not moral perfection. Rather, in his incarnation Jesus entered into all aspects of the human experience, especially suffering and death. Christ experienced what God without the incarnation had not experienced. Christ was complete in knowing human life, not from divine knowledge, but from actual human experience
During this time of Christ’s becoming human in every respect, the ascription of deity, “for whom and by whom all things exist," is appropriately connected to the Father (2.10a, 11a; cp. Phil. 2.6-8).
First let us compare Heb. 2:10 with other New Testament passages that treat of the relation of God and Christ to creation. Of course of the two main creation stories in the Bible, Gen. 2:4b-25 is the older, Yahwistic story, and Gen. 1:1-2:4a is the more recent, Priestly account. All of the New Testament writers simply accept this, and speak of creation by God. The new thing that they bring is that God created the world through Christ. (Note the different prepositions here.) The only point where they differ slightly is that whereas Rom. 11:36 and I Cor. 8:6 (cf. I Cor. 15:28) say that creation is to and for God, Col. 1:16 says it is for Christ.
Secondly, as for the divinity of Christ, just about all the New Testament writers simply seem to accept it. The Gospel of John, written at the end of the first century, makes the most of it. The author to the Hebrews, writing before 70 A.D., seems simply to accept it, writing simply of “Jesus” as “the Son.” His real task is to insist, not on the divinity of Christ (which, as said, he simply accepts), but on Christ’s superiority to angels, Moses, Aaron, and indeed all foregoing priests, and thus to the whole old Mosaic dispensation with all its rules and regulations about sacrifice etc. The author to the Hebrews was no doubt aware of those Christians who wrote before him, such as Paul (but not John), but he is here concerned, not to quote them, but to make his own points about the supremacy of Christ, the importance of not lapsing back into the old ways, and the necessity of keeping the faith (Heb. 11). As such, these points are important for us even today.
The context of Hebrews 2:5-18 underscores the role of God the Father as the source and initiator of salvation through the death of Christ. Specifically, verse 10 expands the reference in verse 9 that "by the grace of God" Jesus suffered death for the benefit of all. Thus the reference to God as the One "for whom and by whom all things exist" in verse 10 explicitly affirms the point that God is creator and preserver of all things. Being such, "it was fitting" that God would rescue humanity from its plight under the dominion of death and the devil, which God accomplished by means including His Son's suffering in solidarity with humankind.
In this context the focus is not the deity but the humanity of Christ, whereas the deity is affirmed in 1:1-12 and directly in 1:8 where the title "God" is attributed to the Son. Although the description "for whom and by whom all things" is not elsewhere said of God the Father, the exchange of divine titles and attributes applied to God and to Christ is not at all unusual but rather precisely part of the substance of the Christological teaching of the New Testament which later necessitated the formulation of the doctrine of the Trinity. In addition to your citations, see Phil. 2:6-11 which ascribes the sacred name of God (YHWH) to Christ and also Rev. 1:8,17; 22:13 where the expression "first and last" is attributed alternately both to God and to Christ.