Fact and Design: You are confusing modalism/oneness/Sabellianism/Jesus only heresy (google it) with trinitarianism (common WT rookiei mistake). Oneness says that Jesus is Jehovah/God and that He is the person of the Father in the NT, the person of the Son on earth as a man, the person of the Holy Spirit in the Church Age. So, Jesus is God and He is one person who steps into different offices/modes. This is an easy heresy to refute (WT is right to say that who did Jesus pray to? Himself?, etc., but they are refuting modal monarchianism, not trinitarianism).
The triune view does not confuse the nature/substance/essence/being/ontology of God and His personal distinctions. There is one true God, uncreated spirit, YHWH. There are not 3 gods in 1 god; not 3 persons in 1 person. Within the one eternal spirit nature of God are 3 personal distinctions. We can show that the Father is YHWH, the Son is YHWH, and the Holy Spirit is YHWH. We can show that the Holy Spirit is personal, not impersonal ('active force'). We can show that the Father, Son, Spirit are distinct in one sense (each has will, intellect, emotions and relate to each other in love, fellowship, communication). Once we show that Jesus is Creator God, not creature (Deity of Christ) and that the Holy Spirit is personal and Deity, then the triune understanding follows. This is based on revelation and the parameters of Scripture, not reason. 3 gods in 1 god is illogical, but 3 personal distinctions in one nature of God is revelation and not a contradiction. God is compound unity (showing that love, fellowship, communication are eternal and that God Himself can come to earth as a man, not possible if He is solitary). Unitarians, JWs, Jews, Islam sees God as a solitary being. He could be this way, but He has revealed Himself as having plurality within unity (also possible if that is the way He truly is). Just as it is impossible for finite creatures to understand how God has always existed (something usually does not come from nothing), so we cannot exhaustively understand how the one God can be triune, yet He is (based on parameters we do have). Father, Son, Spirit are the one God as to common spirit nature, yet they are distinct as to conscious centers. There is nothing else like God (analogies about one cluster of grapes, one army many soldiers, one family many members, etc. illustrate compound unity, but they are limited; husband/wife are two, yet one; time is past/present/future; water is solid/liquid/gas).
The WT always misrepresents the Trinity. Jews failed to understand progressive revelation. They were right about monotheism, but wrong to reject God's full revelation in Christ given in the NT (Jesus claimed to be God and also taught us about the personal Spirit...hence triune statement in Mt. 28 which does not say in the name of God the Father, the Son Michael the created angel, and the name of an active force, not a person Spirit?!).
Just because someone cannot fully comprehend a doctrine does not make it false. The Bible says that man cannot fully comprehend God. Human reason has limitations, but we cannot compromise revelation (the triune understanding deals with all the evidence, not just some OT verses). The WT book Reasoning from the Scriptures also recognizes that humans cannot understand everything about God. About his eternal nature: 'Is that reasonable? Our minds cannot fully comprehend it. But that is not a sound reason for rejecting it.' This statement can be applied to the trinity which is defensible from Scripture. It would be easier to believe the Jewish or WT view (easier to explain), but it is still wrong and contrary to Scripture (the personality of the Spirit is easy to show; WT says impersonal because of denial of trinity, not because Scripture demands it; the Deity of Christ is also clear in my mind and the few objection verses Arians use can easily be interpreted as non-contrary to this). Books are written defending the trinity and refuting Arianism. How objective are you willing to be?