If (and that's a big if) God created the universe then he could have done the miracles in the Bible and elsewhere. I would agree. However, you're probably using circular logic to bolter your faith. If you're like most people, you read the Bible treating the miracles as factual demonstrations of God's power. If God can do the things in the Bible and in the lives of people you know then he's very powerful, powerful enough, perhaps, to create the Earth, etc. The logic is circular.

On the other hand, if the miracles reported by believers did not occur (and scientific studies suggest they did not) then we are left with little evidence that God can do miracles and, thus, that He could have created the Earth or anything else.

If science can explain the universe without God, then what need is there in that hypothesis?