This question has multiple parts so let me deal with each one.
First, there appears to be little dispute about the Hebrew text of Ex 33:19, which says (literally NASB is a good version here):
And He said, "I Myself will make all My goodness pass before you, and
will proclaim the name of the LORD before you; and I will be gracious
to whom I will be gracious, and will show compassion on whom I will
show compassion."
Second, as correctly suggested in the question, there is also no debate about who the antecedent of "he" is here - it is the LORD, namely, YHWH - Jehovah Himself. This was actually done and recorded in Ex 34:5-8 which says:
And the LORD descended in a cloud, stood with him there, and proclaimed His
name, the LORD. Then the LORD passed in front of Moses and called out:
“The LORD, the LORD God, is compassionate and gracious, slow to anger,
abounding in loving devotion and faithfulness, maintaining loving
devotion to a thousand generations, forgiving iniquity, transgression,
and sin. Yet He will by no means excuse the guilty; He will visit the
iniquity of the fathers on their children and grandchildren to the
third and fourth generations.”
Moses immediately bowed down to the ground and worshiped
Third, this means that we have the LORD proclaiming the name of the LORD. This sort of thing is not unique in the OT. Here are several more examples that provide further support for YHWH being more than one person but still being ONE.
- Zech 2:6-12 – the LORD (= YHWH) claims three times that He has been sent by the LORD.
- Isa 48:11-16 – again, the LORD has been sent by the LORD.
- Isa 63:7-10 – the LORD (described as a Father) sends His divine servant (the angel of His presence) and His Holy Spirit who is grieved (compare Ps 78:40).
- Ex 23:20 – the angel of the LORD’s presence has the power to forgive sin (but will not). This and the previous reference clearly make the angel of the presence the pre-incarnate Jesus.
- Hos 1:7 – the LORD saves by the LORD their God.
- Prov 30:1-4 – the Son of God is as unfathomable as God Himself.
- Psalm 110 – “The LORD says to my Lord” – Jesus asked about this Psalm on how someone could be both Son and Lord of David – see Matt 22:44, Mark 12:36, Luke 20:42, Acts 2:34.
- Ps 45 (quoted by Heb 1) talks about the “Son” being God in addition to God the Father.
- Gen 1:1, 2, 26, 11:6, 7 – God refers to Himself in the plural.
There are still more examples that could be quoted under the general heading of the Angel of the LORD actually being the LORD and probably (preincarnate) Jesus such as: Gen 16:7-13, 22:11-17, 32:24-30, 48:16, Ex 3:2-6, 32:34, Num 22:22-35, Josh 5:13-15, Judg 2:1-4, 6:11-23, 13:3-23, Isa 63:9, Dan 3:25, 28, Hos 12:4, 5, Zech 3:1-7, Mal 3:1.
A closely related phrase, “Angel of God” who is clearly God as in Gen 6:13, 8:15, 9:8, 17, 15:13, 17:3, 4, 21:12, 16-21, 35:1, 10, Ex 4:3-8, 6:2, 23:20, 21, Deut 1:6, 1 Kings 12:22, etc. See also Acts 10:3, 4, Ga 4:14.
Thus, unsurprisingly, Jesus is the messenger to the human race and underlines the importance that the Godhead places upon such messages.
(This is not to suggest that Jesus is an angel in the sense that He is less that God; far from it! However, the Greek and Hebrew word for “angel” simply means messenger and it is in this sense that Jesus is the messenger in the above passages.)
For completeness I list the text of the LXX at this point. Note that the LXX as we now have it does not always reflect the Hebrew text we now have - they are sometimes are sometimes noticeably different because either the LXX uses a different Hebrew text or reflects bias on the part of the LXX translators.
καὶ εἶπεν· ἐγὼ παρελεύσομαι πρότερός σου τῇ δόξῃ μου καὶ καλέσω τῷ ὀνόματί μου, Κύριος ἐναντίον σου· καὶ ἐλεήσω ὃν ἂν ἐλεῶ, καὶ οἰκτειρήσω ὃν ἂν οἰκτείρω. = And he said, I will pass by before thee with my glory, and I will call by my name, the Lord, before thee; and I will have mercy on whom I will have mercy, and will have pity on whom I will have pity.
