Unfallen Angels are called sons of God in the Old Testament.
Representive angel? There are many passages where the Angel of the Lord is clearly the pre-incarnate Christ. That is a big area of theological difference!
As the original example so too are the assumptions and substitutions in regard to the angel of the Lord. "Because it fits" is not sufficient reason. Particularly when Hebrews makes it clear that no angel is a son. There needs to be more than that to build doctrine on. In regards to the angel of the Lord, it is more appropriate to simply consider him the Lord's personal representative angel, as Matthew 28 shows plainly they are not the same.
Hebrews 1:5 For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son?
Hebrews 1:13 But to which of the angels said he at any time, Sit on my right hand, until I make thine enemies thy footstool? 14 Are they not all ministering spirits, sent forth to minister for them who shall be heirs of salvation?
Matthew 28:1-5 In the end of the sabbath, as it began to dawn toward the first day of the week, came Mary Magdalene and the other Mary to see the sepulchre. 2 And, behold, there was a great earthquake: for the angel of the Lord descended from heaven, and came and rolled back the stone from the door, and sat upon it. 3 His countenance was like lightning, and his raiment white as snow: 4 and for fear of him the keepers did shake, and became as dead men. 5 And the angel answered and said unto the women, Fear not ye: for I know that ye seek Jesus, which was crucified. 6 He is not here: for he is risen, as he said. Come, see the place where the Lord lay. 7 And go quickly, and tell his disciples that he is risen from the dead; and, behold, he goeth before you into Galilee; there shall ye see him: lo, I have told you. 8 And they departed quickly from the sepulchre with fear and great joy; and did run to bring his disciples word.
Who ever refers to a pastor as an angel of a church? These angels are literal angels.
Galatians 3:19- Wherefore then serveth the law? It was added because of transgressions, till the seed should come to whom the promise was made; and it was ordained by angels in the hand of a mediator.
Galatians 1:8- But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
Some particular encounters of angels are the Angel of the Lord (in the OT) - which is sometimes (or most of the time) Christ. In Revelation, I believe there is at least one reference to an angel which is Christ (based on the description and what that angel does and the timing of the event - ch 10 fits Christ having the book given Him in chapter 5, and landing on the earth, reclaiming the earth at the end of the seven year tribulation period).
If at least one reference to an angel in Revelation is not a physical angel (but Jesus), then why couldn’t chapters 1-3 be something other than a literal angel? Matthew 11:10; Mark 1:2; Luke 7:27 uses the Greek word for angel to refer to John the Baptist. Luke 7:24 and 9:52 and James 2:25 refer to human messengers. So there are definitely examples of that word referring to non-angelic messengers (ie. humans).