I can only comprehend God’s act of existence in a very general sense. God exists because of his nature, something about his nature means that he is necessary or cannot not exist.
A brute fact does not exist because of its nature, it just exists for no reason. For example, to argue that a contingent being or a series of contingent beings just exist would be an argument for a brute fact because clearly a contingent nature does not exist because of its nature; it exists for no reason at all.
You want me to comprehend the essence of God or otherwise i cannot posit the existence of a necessary cause or say that the universe is not a necessary cause. But this is a fallacy, a straw-man, and a game of semantics. Anything can be said to be a brute fact, but not anything can be coherently be said to be necessary, contingent beings included…
Until you comprehend that a brute fact is not in principle the same thing as a necessary nature, i suppose that you won’t find the arguments convincing, but i don’t think that’s got anything to do with the arguments themselves.