All of your questions are related, for you seem to be suggest that because evolution sometimes causes things that prove counter-productive for the survival and well being of humans, then God is somehow implicated in moral wrongdoing.
First off, it is of Catholic teaching that the Universe was deliberately set up in a state of journeying: It is not yet perfected. No matter how literally one takes the creation account and story of the Fall of man in Genesis, ultimately the Catholic faith believes that God intentionally created an imperfect creation, only to be consummated in the “New Heavens and New Earth.”
But why did God not create a world so perfect that no evil could exist in it? With infinite power God could always create something better. But with infinite wisdom and goodness God freely willed to create a world “in a state of journeying” towards its ultimate perfection. In God’s plan this process of becoming involves the appearance of certain beings and the disappearance of others, the existence of the more perfect alongside the less perfect, both constructive and destructive forces of nature. With physical good there exists also physical evil as long as creation has not reached perfection. CCC#310.
Can we know a bit more about why God would allow this? It seems he prefers the freedom of his creatures. And by this I don’t just mean “free will,” but the very inherent goodness God has given to his creation to work for its own purposes, which ultimately are tied to God’s purpose.
God is the sovereign master of his plan. But to carry it out he also makes use of his creatures’ co-operation. This use is not a sign of weakness, but rather a token of almighty God’s greatness and goodness. For God grants his creatures not only their existence, but also the dignity of acting on their own, of being causes and principles for each other, and thus of co-operating in the accomplishment of his plan. CCC#306
Now humans are central in God’s creation. But Catholicism also professes that has created all things with inherent goodness. The snake you mention may sometimes bite the human, or even kill him. But the snake is good and has its own place in creation as well.
At the end of the day, we don’t know enough about why this or that virus was allowed by God. But what we DO KNOW is that the human species has only formed after millions of years after Earth even formed. Therefore, it seems that everything has worked together to ultimately bring about the human race.
To take an example. I thought of this a few months back. Some scientists believe that one mass extinction with the dinosaurs took place because a meteor struck the Earth. That’s very unfortunate and was a physical evil, causing death and destruction for many organisms. But without that seemingly unfortunate event, we most certainly wouldn’t even be here.
On the one hand, God see absolutely everything from His “eternal now.” He knows everything that must happen for the human species to event get kickin’ in the first place. But he also respects the “freedom” of his creatures. Nature is nature, but God’s ultimately in control.