Sorry, don't have easy internet access for the next few days. Will reply properly when I can. What I will say is my understanding of the point about exhaustiveness is that it is a conclusion from Platonic metaphysics, though only the basic metaphysics such as the forms, the one and the dyad, etc. It would be strange if said metaphysics fell into the problems you mention, seeing as it is the foundation of one version of the first way. I also don't know if panentheism is the best term. It is not one I like. In this matter, it is little different to the Palamist and general Orthodox belief that all things are in God in some sense. There are, after all problems in totally separating God and creation. Catholicism is influenced heavily by said metaphysics. I am not sure if it can be supported on pure Aristotelianism or other metaphysics, though there is close links between Platonism and the former. Traditional Christianity, including Catholicism and even Scholasticism, have been heavily influenced by Platonism. The situation is different to, say, Kantianism. The Catholic would have to consider whether his position commits him to serious questions here.