Hope you are well. I am so much pleased that you are studying seriously our Krishna Consciousness philosophy. Please continue with your sincere efforts for Krishna. Now, regarding your question about Brahma, he may be chosen either from the liberated or the conditioned souls. In this case Brahma is a liberated soul from the beginning; therefore there is no contradiction that Brahma can be Haridasa Thakura. Those who are conditioned souls are eternally so, which means that it is never possible to trace out how long ago the conditioned existence began. We simply say that misuse of the little independence we have got creates so much trouble for us. But now by adopting Krishna Consciousness, we may finish this conditioned life immediately. That is Krishna Consciousness.
Your reasoning is all right that the Brahma energy must have conscious direction to manifest form. Therefore He who gives that direction is the Ultimate Controller or Param Isvara. In Brahma Samhita it is said: "Isvarah paramah krsnah saccidananda vigrahah, anadir adir govindah sarva karana karanam (Bs. 5.1)." Krishna is the Supreme Controller of all controllers and therefore, He is the Origin of everything including the Brahma Energy. This Govinda is the cause of all causes, and He is without any cause. This is the beauty of the sastras, that one sloka finishes billions of years hard labor of mental speculation. Just try to give evidence like this.
Regarding the Christian's Trinity, I believe it is called God, the Holy Ghost, and the son. Person in Krishna Consciousness accepts this by the name Visnu, Paramatma, and Jiva. God is a Person, the holy spirit or the supersoul is a person, and the living entity is also a person. Also, Mary is the representation of the energy of God. Either as internal energy Radharani or as external energy Durga, the energy of Godhead can be considered the mother of the living entities. But there is no clash between the Bible and the Vedas, simply some people formulate their personal ideas and cause quarrelings. Nobody can say the Bible was meant for the same class of men as the Bhagavad-gita. And Bhagavad-gita is the ABC's of spiritual knowledge. Beyond that is Srimad-Bhagavatam. How great Srimad-Bhagavatam is nobody can imagine. And beyond that is Caitanya Caritamrta. But beginning from the Bible or Koran, on up the principle remains the same.