The Godhead is undivided in substance, but divided in person. This is the explicit teaching of the scripture, such as John 1:1 where it says "In the beginning was the Word, and the Word was with God, and the Word was God." Thus the Word is both separate ("with God") and united ("was God"). These are not two gods, but two persons (three with the Holy Spirit) who are but one God.
From Swedenborg: God's Omnipotence, Omniscience, and Omnipresence
Speaking of omnipotence, Christ is called "almighty" in Revelation. There cannot be two almighties (a father and a son separate almighty), but only one Almighty. Thus these three (the Father, Son and Holy Spirit) are one.
Rev_1:8 I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty.
Does Jehovah not mean 'The Father?
Jehovah means "self-existent one", IOW, one who is not created.
For in Him dwells all the fullness of the Godhead bodily; 'Godhead' is Godhood or Godness. In other words, ALL Divinity is present within Jesus Christ.
Yes, indeed. This proves his divinity, not His created status.
Person here from that Catholic creed is translated from persona which can mean some sort of mask. For me, Jehovah being the Lord Jesus' soul and the Holy spirit being the Lord's proceeding (action) makes a whole lot more sense. We are in the image and likeness of God. I can relate to that.
Isaiah 49:11 For My own sake, for My own sake, I will do it; For how should My name be profaned? And I will not give My glory to another. God’s Ancient Plan to Redeem Israel 12 “Listen to Me, O Jacob, And Israel, My called: I am He, I am the First, I am also the Last.
From the Bible Study in the original post, it is explained how the infinite and finite coexisted within Jesus up until his death and Glorification (whereby he became fully infinite and un-created - 'One with the Father', but He also claims that during His lifetime, in Scripture). That's what makes sense to me.
As an aside, in the Bible: Jehovah means the Lord in respect to Divine good, while God means the Lord in respect to Divine truth.
A recent article on this is at: The true one-ness of the Trinity