I think a logical case can be made for the existence of God from the beginning of the universe

Okay, I am an atheist. But I have had a think about what the universe could have come from and I have decided based on pure logic that the best explanation of its existence is a creator. Here is my argument; we know all events in nature are caused, this is a fact which every metaphysician accepts. The Big Bang was an event. Therefore, the Big Bang must have had a cause. Now that cause can be logically shown to have been operating outside the spacetime we know gives time for things to happen in. It also had to be not made of stuff because matter and antimatter constantly annihalated each other in the primeval period of the Big Bang when they were all that existed. Therefore in sum no matter existed at any point at t=0 when the Big Bang occured. So we know something transcendent had to exist to give rise to the universe.

Formally, my argument could be stated like this

1. events must have causes

2. the Big Bang was an event

3. therefore, the Big Bang had a cause or causes

4. since the Big Bang had a cause or causes something or a number of things immaterial and outside spacetime had to form it

5. therefore, at least one God-being exists

Critiques?