I’m way behind on posts to a variety of folks, so I’ll limit it to this:
You say “that the Godhead in heaven consists of the father and the son and the holy spirit is their presence in our world.”
If the Holy Spirit was an it, your case would be better. But He is He, and yet not God the Father or Jesus, since Jesus said, “Nevertheless, I tell you the truth: it is to your advantage that I go away, for if I do not go away, the Helper will not come to you. But if I go, I will send him to you.”
and, “But the Helper, the Holy Spirit, whom the Father will send in my name, he will teach you all things and bring to your remembrance all that I have said to you.”
Notice it isn’t Jesus, since He is sent in Jesus name (a phrase meaning to come to do what Jesus would do if Jesus was here), and He isn’t God the Father, since the Father will send Him.
Hence a third person, who is also God.
I did say that, but I also used a lot of scripture to bolster my case.
If the Holy Spirit was an it, your case would be better. But He is He, and yet not God the Father or Jesus, since Jesus said, “Nevertheless, I tell you the truth: it is to your advantage that I go away, for if I do not go away, the Helper will not come to you. But if I go, I will send him to you.”
The holy spirit is also the spirit of Christ and he (jesus) did have to return to his position in the Godhead to send forth his spirit.
As far as "he" and "it" these are english translations of greek gender identification.
In most cases the proper, grammatical way to translate a reference to the holy spirit is "it" because in greek it's a neuter term.
and, “But the Helper, the Holy Spirit, whom the Father will send in my name, he will teach you all things and bring to your remembrance all that I have said to you.”
In this verse, the term "helper" is parakletos which in greek is male gender word...but that doesn't always mean that it's referring to a male of a species. Greek, like French, refers to non-human and non-animal objects as male, female or neuter. It has little or no bearing on the actual "sex".
Translators, influenced by the belief that the holy spirit IS a "he" will translate a gender neutral term as "he."
Here's a good lesson about that. The trinity doctrine was developed over time by the Catholic church. After the reformation, protestant scholars most referred to the holy spirit correctly by using the gender neutral "it".
For example, Romans 8:16 is translated in various ways by different translators:
(ACV) The Spirit itself testifies with our spirit, that we are children of God.
(ASV) The Spirit himself beareth witness with our spirit, that we are children of God:
(BBE) The Spirit is witness with our spirit that we are children of God:
(CEV) God's Spirit makes us sure that we are his children.
(CJB) The Spirit himself bears witness with our own spirits that we are children of God;
(DRB) For the Spirit himself giveth testimony to our spirit that we are the sons of God.
(EVID) The Spirit itself bears witness with our spirit, that we are the children of God:
(ECB) The self-same Spirit co-witnesses with our spirit, that we are the children of Elohim:
(Geneva) The same Spirit beareth witnesse with our spirit, that we are the children of God.
(GNB) God's Spirit joins himself to our spirits to declare that we are God's children.
(GW) The Spirit himself testifies with our spirit that we are God's children.
(ISV) The Spirit himself testifies with our spirit that we are God's children.
(KJV) The Spirit itself beareth witness with our spirit, that we are the children of God:
(LITV) The Spirit Himself witnesses with our spirit that we are children of God.
(MRC) The Spirit Himself bears witness with our spirit that we are children of God,
(MKJV) The Spirit Himself bears witness with our spirit that we are the children of God.
(NET) The Spirit himself bears witness to21 our spirit that we are God's children.
(NSB) The Spirit itself (Greek:autos ho pneuma) (itself the Spirit) bears witness with our spirit (mind and heart), that we are children of God.
(NKJV) The Spirit Himself bears witness with our spirit that we are children of God,
(RV) The Spirit himself beareth witness with our spirit, that we are children of God:
It should be evident, perhaps with more study, that the decision to translate the holy spirit as "it" or "he" is almost entirely dependent upon the belief of the translator.