Isaiah's name, Yeshiyahu means God is Salvation.
Jesus' name, Yeshua, means the Salvation of God.
In the Old Testament God teaches that He is the Husband of His people.
In the New Testament we are taught that Jesus is the Husband of His people
In the Old Testament God says "I am your Salvation."
In the New Testament we learn that Jesus Christ is the Salvation of God, our Salvation.
In the Old Testament God declares He is our King.
In the New Testament, we are taught Jesus Christ is our King.
None of the above conflicts. If you need Scriptural proof, read Isaiah 9:6 where the prophecy of the Child mentions He will be called God Almighty, Everlasting Fasther, Ruler of Peace, Wonderful, Counselor and more.
Yes the Old and the New Testament do say the same thing. It is too bad many here cannot go back to the time right after Christ ascended to the Right Hand of Power to learn from the Tanakh as all new in Christ did learn.