Is Israel God’s firsborn son (Exodus 4:22) or Jesus (Hebrews 1:6)? My understanding is it’s both but in different senses. Would this be correct? In what sense is Israel God’s firstborn? Is it in the sense that Israel was chosen among the nations? In what sense is Jesus God’s firstborn? Is it in the sense of being the chosen Messiah? Or Jesus’ resurrection? Or in another sense?
Yes, absolutely. You have it right. There are many biblical examples of God using a metaphor, a title or a name for two different people or groups of people. The “twelve” can be the twelve sons of Jacob or they can be the apostles. Jesus is called David in the gospels because David is a prefigure of Jesus. The “suffering servant in Isaiah, mentioned dozens of times between Isaiah 40-66 is both Israel and Jesus. In Ezekiel 36 and 37, the prophecies concerning God’s people are both of Judah and the Church.
The same general idea applies to the Old Testament use of the metaphor of firstborn son. For the Jews, a firstborn son is the favored one. He is the one who receives the inheritance. Figuratively, both Israel and Jesus are therefore called by God his firstborn son. Israel is the one specially chosen by God. Israel is the recipient of the Old Covenant, and the promises given to Abraham. Jesus also, but in an even greater way, is God’s firstborn son. He inherits everything. He is the special Son. He is also the firstborn from among the dead (Collosians 1:18). He is the firstborn over all creation (Collosians 1:15) It seems from your comments that you pretty much already understand this!