IIRC, isn't that similar to Aquinas' argument about the Unmoved Mover? One of his proofs of God's existence (or rather a philosophical argument for the existence of God) was an application of Newton's Third Law of Motion: if every action must have an equal and opposite reaction, then every moving object must have been unmoving at some point, and imparted motion by another force. Extrapolated backward in time, you necessarily arrive at a point where an object induced motion, but was not moving itself. The Unmoved Mover. What force could this possibly be but God?
You're thinking of Aquinas'
First Way to prove God's existence, but you've not got it right. It's nothing to do with Newton's Third Law - it would be amazing if it were, given that Aquinas lived over four centuries before Newton worked it out - and as an Aristotelian, Aquinas would not have agreed with it.
The argument has nothing to do with temporal causal sequences. It's about motion being imparted to the universe
right now. Aquinas is thinking of the universe as rather like a train of carriages, each one pulling the one behind. There must be a locomotive at the front of the train, or the overall motion is unexplained. Similarly, there must be a First Mover which is effectively powering the universe, like the spring in a watch.
By the way, what is your opinion of this and Aquinas' other arguments like it? I believe there were five.
The argument is fine as long as you accept the metaphysics, which few people probably would today (outside Catholic scholastic circles, anyway). But a more fundamental problem with it is that even if it works, it doesn't prove God's existence, it only proves the existence of a First Mover. And why would that be God? It could be some purely physical process within the universe. Moreover, it wouldn't have to be the same First Mover all the time.
Somebody (Berkeley, maybe? I can't remember) posited that God could only know perfect things, since he is perfect and if he were to think about imperfect things, then he would become imperfect himself, and thus cease to be God. This was used to explain why God could never interact with the universe, because existent things are necessarily imperfect. Obviously this doesn't fit with the omniscient definition of God, unless we are to imagine that God knows of the imperfect things and simply chooses to never think of them, so as to preserve his perfection. Perhaps knowledge of omniscience is something God possesses, but has not experienced? Does that count as knowledge? Or is God expected to know what all possible experiences are as part of his omniscience?
I don't think Berkeley said that, and he hardly could have, given that he thought that all material objects, perfect or imperfect, exist only within God's mind. The idea you describe sounds more like Middle Platonism. Plato had thought that for every kind of thing that exists, there must be an immaterial Form, which explains the similarity between different individuals of that kind. The Middle Platonists thought that these Forms were ideas in the mind of God. But they thought that there were Forms only of natural things, not artificial ones, and only of good or beautiful things, not of lowly or ugly ones, because these would be unworthy of the divine mind. So the whole concept of the Forms had changed from a basically logical one (in Plato) to a much more religious one (in the Middle Platonists).
Augustine thought that God's mind contained ideas of all things, or at least all natural things, since it was by these ideas that he created them. This was the view of the medieval theologians too, who like Augustine also thought that human knowledge is dependent upon the divine ideas, which directly illuminate the human understanding. At least, they did until Aristotle's much more sensible epistemology was rediscovered.
Modern philosophers - at least after the odd renaissance of Augustinian Platonism that happened in the seventeenth century - would, I think, typically think in terms not of God knowing "things" (perfect or imperfect) but of God knowing facts. God's omniscience means that he knows everything that's true, or at least everything knowable that's true. Whether the facts are positive or negative isn't really here or there.