And here's some verses that helps show that "God's begotten Son" refers to Jesus:
1 John 5:20
20 And we know that the Son of God is come, and hath given us an understanding, that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life.
KJV
John 3:16
16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
KJV
And notice how the High Priest claimed that Jesus was worthy of death by claiming to be "the Son of God" - meaning "God."
Matt 26:63-66
63 But Jesus held his peace. And the high priest answered and said unto him, I adjure thee by the living God, that thou tell us whether thou be the Christ, the Son of God.
64 Jesus saith unto him, Thou hast said: nevertheless I say unto you, Hereafter shall ye see the Son of man sitting on the right hand of power, and coming in the clouds of heaven.
65 Then the high priest rent his clothes, saying, He hath spoken blasphemy; what further need have we of witnesses? behold, now ye have heard his blasphemy.
66 What think ye? They answered and said, He is guilty of death.
KJV
This shows that their law system imposed a death sentence upon anyone claiming to be God. Their problem was that they didn't know He was God. So that's why they thought He was guilty of that crime
Also, notice below, how God's Spirit is addressed as "Jesus" - several times in the Bible in reference to miracles that took place through God's power:
Acts 3:16
16 And his name through faith in his name hath made this man strong, whom ye see and know: yea, the faith which is by him hath given him this perfect soundness in the presence of you all.
KJVActs 3:16
16 And his name through faith in his name hath made this man strong, whom ye see and know: yea, the faith which is by him hath given him this perfect soundness in the presence of you all.
KJVActs 3:16
16 And his name through faith in his name hath made this man strong, whom ye see and know: yea, the faith which is by him hath given him this perfect soundness in the presence of you all.
KJV
Acts 3:19-20
19 Repent ye therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord;
20 And he shall send Jesus Christ, which before was preached unto you:
KJV
Comment: The passage above refers to the fact that God's Spirit is also referred to as the Spirit of Jesus. Jesus was no longer on the earth, at this point.
John 14:17-18
17 Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
18 I will not leave you comfortless: I will come to you.
KJV
Comment: See here, how Jesus said He would come again to them in a form that could be in them? Meaning, He'd be able to communicate with them and help and guide (Romans 8:14) them in daily life, without His being physically present with them.
John 14:16-17
16 And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever;
17 Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
KJV
Comment: See how He had to be absent from them in order to be able to be present with them just in the form of God's Spirit?
Rom 8:14
14 For as many as are led by the Spirit of God, they are the sons of God.
KJV
Comment: Here you can see how sometimes God's Spirit is just called "The Spirit of God?" - in the Bible. Another important fact that this verse brings out, is that no one can born of God (esteemed by God as being His own, and headed for eternal life in heaven after this life), wthout being led by God's Spirit.
Rom 8:15-17
15 For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father.
16 The Spirit itself beareth witness with our spirit, that we are the children of God:
17 And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together.
KJV
Comment: Those who serve God - belong to HIm and God promises them eternal life in heaven with Him after this life - John 3:15.
Gal 4:5-7
5 To redeem them that were under the law, that we might receive the adoption of sons.
6 And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father.
7 Wherefore thou art no more a servant, but a son; and if a son, then an heir of God through Christ.
KJV
Comment: Those who have God's Spirit guiding their lives, belong to Him, and are heirs - meaning they will inherit the riches of eternal life with God in heaven after this life is over.