Two points,
Being part of the Godhead does not mean that the independence of it's entities are sacrificed. So, the knowledge of His return being known only by the Father is consistent.
The Father is from whom the Son and the Spirit flow. Yet they and the Father are the Godhead, and one in that context. One God.
There is clear independence and distinction between the Son and the Father. Jesus does not know of the time of His Return, the Father does.
Jesus calls out when dying on the cross to the Father:
And about the ninth hour Jesus cried with a loud voice, saying, Eli, Eli, lama sabachthani? that is to say, My God, my God, why hast thou forsaken me? Matthew 27:46
Further Jesus is subservient to the Father:
I can of mine own self do nothing: as I hear, I judge: and my judgment is just; because I seek not mine own will, but the will of the Father which hath sent me. John 5:30
You heard me say to you, ‘I am going away, and I am coming to you.’ If you loved me, you would rejoice that I am going to the Father, because the Father is greater than I.
John 14:28
So for the trinty to work, Jesus must be both seperate and independant of God and yet be part of God at the same time. That leads to the importance of emphasising the Divinity of Christ. I have no issue with that but there are clearly limits due to the clear distinction between the Father and the Son.
With respect, it appears as though you are trying to reconcile the Christian Godhead with other faiths, and the triune nature of God cannot be reconciled with these other faiths.
So either the truth of Christianity stands alone, or it must be denied or modified so it fits with these other faiths.
As the Hebrew Bible is reconciled with the New Testament so too is the Quran reconciled with both books and beyond that the Baha'i Writings. It is simply my belief that God has Revealed Himself through the Jewish Prophets, Christ, the apostles, Muhammad, the 12 Imans then the Bab and Baha'u'llah. This is progressive Revelation as God's unfolding purpose to humanity made clearer with successive Revelations. I believe they can be reconciled as you believe in the New Testament and Hebrew Bible alone and successive Revelations can't be reconciled. I'm not here to change your mind but as you are clear about what you believe, I too am clear about what I believe.
In regards the trinity, I see no problem whatsoever. Judasim and Islam have no need for the doctrine. The trinity isn't mentioned at all in the New Testament and is clearly a man made doctrine formulated over a few centuries until it was crystalised into its current form over the 4th centuries. It appears the main reason it has existed largely unchallenged for so long after the establishment of the revised (Constantine) Nicene Creed was because of the risk of severe repercussions with Church authorities. The reformation didn't really challenge it. It wasn't until the enlightmentment era in Europe and the development of new Christan movements from the nineteenth century when a significant challenge has emerged within Christianity itself.
I agree the word Godhead appears in the Bible but only on three occasions (Acts of the apostles 17:29, Romans 1:20 and Colossions 2:9) and only in some early English translations of the Bible at a time the trinity was unquestioningly accorded with the same status as Word of God itself. Newer translations don't use the word.
In Genesis the plurality of God is stated. The first book of the Bible. When Christ said, "before Abraham, I am", He made it clear that He was part of that plurality.
Though the word trinity is not used, the word Godhead is. This word supports the plurality of God.
The word Elohim can apply to god or gods that are not Yahweh too, for example Exodus 20:3. It can also apply to Yahweh as a singular Noun (Exodus 3:4).
The Phrase 'I Am' is linked to God Himself but in the context of His Revealing Himself through Moses (Exodus 3:14). So 'I Am' used in John 8:58-59 appears to be Jesus equating Himself with God (I am) revealing Himself through Moses. That would have been sufficient cause for some in the audience to pick up stones.
As a Christian, it is clear to me that Christ was God incarnate on earth. When He said "no man comes to the Father, but by me", the exclusivity of the Gospel is firmly established. One cannot come to the Father by Mohammed, or in fact by any other faith if one accepts Christ at His word.
Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me.
John 14:6
There are two meanings I see in this verse.
1/ It was the week leading up to Christ’s crucifixion and Jesus had just predicted His imminent martyrdom. So Jesus was comforting His disciples in reminding them He was the Promised Christ. His audience was exclusively Jewish and so was about fulfilment of prophecy in the Jewish Bible.
2/ We have another 'I Am' statement where Jesus reinforces His status as being the same status as Moses and it is God who speaks through Him.
The statement is not a rejection of Muhammad as Muhammad wasn't born until 570 AD. It is the clear duty of any follower of Christ to reject false Prophets but also accept the true Prophet when He Reveals Himself. Muhammad was such a Prophet.
That is how I see it.
Christ was either insane, a charlatan of the highest order, or exactly who He said He was.
Denying His words, like "if you have seen me, you have seen the Father" or " I and the Father are one", and all the other evidence for His being God incarnate, makes him out to be either an insane liar, or a crooked one.
I have no problem with the Divinity and Sonship of Jesus. I simply understand it differently to some Christians.
This may make Christ more acceptable to other faiths, but He made clear that their acceptance of Him as anything other than but who He truly is, is irrelevant.
The two Faiths that accept Christ as a Prophet and Messenger from God are Islam and the Baha'i Faith. Islam rejects the NT and Hebrew Bible as corrupted and superceded. The Baha'i Faith does not.
Peace.