What is the significance of Moses being called a “bridegroom of blood?”

In sensus plenior, the whole of chapter four is a hidden narrative of Christ and the cross. It hints at a conversation between 'the Lord' and 'my Lord' as David recounts.

   Ps 110:1 A Psalm of David. The LORD said unto my Lord,...

The first part of the chapter is a conversation about the Son becoming incarnate and being made to be sin. At first he doesn't want to do it because the idea of being made to be sin is abhorrent to him. (Moses and the rod turned serpent). This part of the conversation is also reflected in the parable of Matt 21:28-31.

Verse 20 is his incarnation.

In prophetic riddles, when someone is threatened with death but does not die it is a symbol of the death and resurrection of Christ. This occurs within the passage in question.

At the cross, Christ is obtaining his spiritual bride, the church. Zipporah represents Israel, the first bride of flesh. Like Leah and Rachel.

The first wife is imploring Christ not to forget her, and to remember the covenant. Since "Life is in the blood" She says "You are a husband of life to me."

In SP:

   Exod 4:25 Then [Israel] took [the word of God], and [remembered the promise made to Abraham], and [prayed], and said, Surely a husband [of life] art thou to me.

   Exod 4:26 So he [rose from the dead]: then she said, A husband [of life] thou art, because of the [remembered promise].

Please let me know if more details are needed in the transformation.