I agree with much of what you've said, but I think your idea that the doctrine of the Trinity originated with a pagan three-headed god is a bit far out. It would be far more accurate to attribute the doctrine to the influx of Greek philosophy. Most of the learned men of that time -- the men who actually established the doctrine of the Trinity -- had been educated in Greek schools where neo-platonism was the commonly accepted means of defining the world, man, and God. By the fourth century, the Church was pretty well steeped in Greek culture, and it was according to Greek philosophical thought that the scriptures were interpreted. It was difficult for someone trained to think in metaphysical terms to to understand scriptures. As a matter of fact, it was far easier to simply ignore what the scriptures said about God when they didn't fit the neo-platonic mold of what God supposedly had to be. The first-century Christians had a far more accurate understanding of (1) the nature of God, (2) the relationship between God the Father and His Son Jesus Christ and (3) the relationship between the human and the divine than their fourth century counterparts.
Again, I agree with you up to a point. There are literally dozens of scriptures than simply cannot be understood when you attempt to interpret them by trinitarian logic. I could provide example after example, as I'm sure you could, that simply don't make sense if you see the Father and the Son as both being parts of a single, invisible substance. They are two separate individuals, physically distinct from one another. They are "one" in terms of their unity of will and purpose. They think and act as "one," but they are not physically "one."
At the point where you described the Holy Spirit as "God's Active Force," you kind of gave yourself away. The only Christian denomination I am aware of that uses this terminology is the Jehovah's Witnesses. For some reason, the JWs don't seem (at least generally) to like to divulge their denomination on this forum. Maybe its out of fear of being ridiculed. That doesn't happen a lot on this forum, incidentally. People who cannot respect one another's differences are generally just asked to leave. So, if you are a JW, I would appreciate your simply admitting it. If you're not, would you mind explaining your use of their unique terminology.
I don't believe that the Holy Ghost (this is the term I personally prefer) is the third member of the Godhead mentioned in the scriptures. I believe that, unlike the Father and the Son, He is an unembodied spirit. In a sense, this makes Him God's active force, but He too is separate from God the Father, because God the Father, like His Son Jesus Christ, also has a spirit of His own. The Holy Ghost is the means by which the Father communicates to mankind. Since the Spirit is physically omnipresent (unlike the Father and the Son who physically reside in Heaven), He can be present wherever He is needed to reveal God's will to man. He is a Comforter, a Revelator and a Teacher who exists apart from the Father and the Son.