Theodosius was not repairing any schism. He declared Nicene Christianity as the official state religion of Rome and anyone declaring a different flavor of Christianity to be the right one was in trouble. What exactly this Nicene Christianity consisted of was not decided until the following year. This was not a reconciliation move. This was a ‘my way or the highway’ statement. And the highway could lead to some really bad places. The 381 Creed was just that a Creed, not a detailed theology. It was something short enough to memorize and to declare on demand as a sort of Pledge of Allegiance.
There is no mention of persons in either form of Nicene Creed. That does not appear until De Trinitate in the 5th century. The 381 Creed is still compatible with subordinationism. The Son is begotten by the Father, although eternally and not created in time as Arius claimed. The Holy Spirit proceeds from the Father (and from the Son, although that trouble making phrase may not have been original). The Son is said to be of the same essence as the Father. Not consubstantial as Augustine translates ὁμοούσιον into Latin. This allows thinking that the Father and the Son are the same thing, rather than consisting of the same kind of thing. But that is what Augustine wants to be the case. One of Auguastine’s objectives was to dispose of the still strong hint of polytheism in seemingly having three Gods.
The Milvian Bridge vision in the sky sounds very much like something that Eusebius invented years after the fact of that military victory. Or are you saying that there really is a Sun god that can aid in military success? Coins minted following that battle depict Constantine and a sun god side by side. It is not unusual in Roman and other cultures to attribute victory to divine aid. It is both an expression of humility of piety and at the same time a statement of divinely granted authority, Constantine was definitely not a Christian at that time. He favored Christianity as a political move to reduce the power of the old-guard pagan nobility who were happier when there was a divided empire and less powerful emperors. Constantine did not submit to being baptized until he was dying. Having to live a Christian life is not compatible with exercising total power as Emperor, something Theodosius discovered to his regret years later.
The crucifixion of Jesus and the imagery of the cross as an important symbol in Christianity appears as early as Paul in the mid 1st century and many times afterward in Christian writings. I was raised Catholic and have read extensively on early Christianity. Never have I seen any mention of the cross being thematically connected with the Trinity. It also does not make sense. Why would the crucifixion of the Son be connected with the Trinity? A very misleading image and reminiscent of the Patripassian heresy argued against by Origen in the preceding century and which never had many followers anyway.
Revelation is a big topic but how you are wrong is not for today and we are already far astray from the topic of this thread,
While I was raised in a Catholic family, I don't know the customs of today. In the days of yore, one made the sign of the cross with the phrase, in the name of the father, the son, and the holy ghost. The sign of the cross was intimately connected with the Trinity. As for the false prophet Paul joining the imagery of the cross with salvation, such as in his false gospel of the cross/grace, well, those who follow the ravaging wolves, wind up on the path to destruction (Matthew 7:13-15).
As for the story of Milvian Bridge, I suspect Eusebius, as the court historian, made up both versions. The first being around 312 AD, 1 year prior to Constantine minting his sun god coin, and another once Constantine started pushing his new Roman church. As for Constantine being baptized, that story would have been written by Eusebius, an Arian, and once he mentioned that history was often not true, written falsely for the good of the little people.