Perhaps the whole problem here is our understanding or lack of understanding exactly what or who God is. [How much do we have to know? How much do we have to believe? How much knowledge and how much faith?]
Insisting on dividing Him into three parts or persons or coequal entities in itself causes a problem... a lack of understanding as I see it. For me the Holy Spirit is understood better simply as what men commonly call the Father, or God, or God the Father. Is not God a Spirit and is He not Holy [set apart]? So then why do we insist on two there, the Father and the Holy Spirit, instead of simply taking only what each of us understands from that without bending or turning corners or twisting to find what someone says they found centuries ago? I have never found it!
"Hear, O Israel: The LORD our God is one LORD:" Deut 6:4
"And Jesus answered him, The first of all the commandments is, Hear, O Israel; The Lord our God is one Lord:" Mark 12:29
"Now a mediator is not a mediator of one, but God is one." Gal 3:20
Only in the NT because of the wording of few verses does there seem to be a problem. I could provide an explanation for these and so could others but we know or should know that arguments on those points have been covered hundreds of times over the centuries by many people and they are not likely to change anyone's point of view so easily now.
For the Holy Spirit, called a He [the Father] or an It [a special extension or arm or administration of the Father] is a reality [to me anyway]. The verses I quoted above and others make it clear to most, if not all, of us that there is One God. Why insist on something more because it seems to fit one theory [the one you hold as your own, perhaps?] rather than because it really makes a difference to where we are or want to be in God? Anywhere here is where I am on it:
The functioning of the Holy Spirit [whatever it or he is] as I see it is the way that God brings His Word to Life in people. We eat the flesh of Jesus [read or hear the scriptures] and the Holy Spirit in us quickens that raw dead flesh so that it becomes the Word of God. The Holy Spirit is effectively the Blood of Jesus:
"Not that we are sufficient of ourselves to think any thing as of ourselves; but our sufficiency is of God;
Who also hath made us able ministers of the new testament; not of the letter, but of the spirit: for the letter killeth, but the spirit giveth life." II Cor 3:5-6
The letter is the Bible itself, the dead carcass, the raw flesh of Jesus still dead as it was on the cross without blood.
"Then Jesus said unto them, Verily, verily, I say unto you, Except ye eat the flesh of the Son of man, and drink his blood, ye have no life in you." John 6:53
We read it thus consuming it [the flesh of Jesus who is the Word] but for a man without the Holy Spirit in him it remains at best only wise words, something like the Code of Hammurabi, if that. When however it is quickened [brought to Life] in us by the Holy Spirit then it is written on our hearts as the Living Word of God. It does not come to Life simply because we want it to but rather because God in us, or the Blood of Jesus, or the Holy Spirit, is using what we have and where we are and how surrendered we are to Him to accomplish His purpose in us and/or with us.
I know that this flies in the face of many people because it interferes with their unrelenting attachment to the doctrine of a Trinity. I don't say there is no Trinity, but the Bible certainly does not read anywhere that failure to believe in the Trinity will result in death or no salvation. Some trinitarians concede that. Others do not.
It is nonetheless a part of my vision at present. The vision has changed in the past for each of us as we grow in God.
We really must have a vision, a vision that is improving from "as through a glass darkly" to "face to face".
"Where there is no vision, the people perish... " Prov 29:18
Some now may want to bombard me with their pet trinitarian proof texts as if suddenly I will be changed by their renewed presentation of something I have seen and read in the past more times than I can remember. It is not as simple as that. Only God gives the increase.
Give God the glory!