If the spirit was identical to Jesus, he couldn’t dwell in the heart of Christians because he would have a body.
Jesus says the “Father is greater than I” because there is an order to the trinity.
If you read around those verses you see it’s because God sent Jesus (and also the spirit). (Jn 5:23, 14:25-31) It’s Jesus’ will to do the work of God who sent him. (Jn 4:34) Jesus is just as much God, because he deserves the honour that is due to God (5:23).
Throughout the gospel of John, Jesus says that he is God and that he gladly and willingly does God’s bidding.
It’s hard to understand because we think that if we were God, we could do whatever we want.
That’s actually what Jesus does. The twist is that what he wants, more than anything else, is to do exactly what the Father sends him to do him. The Spirit works in the same sort of way. It’s not demeaning or humiliating. It doesn’t make him less powerful or majestic.
The gospel of John is a good part to read to help with understanding the Trinity. The key idea is that the three are equally God, but not identical.