Is being an atheist a way to absolve oneself for having broken the third commandment?

In a word: no. Your God promises forgiveness if you repent. Why would we, instead of accepting that forgiveness, "pretend" to not believe in him, which is a much bigger sin? It's absurd. We don't believe because all the evidence people point to falls incredibly short of even suggesting the existence of ANY deity, let alone the Christian God versus the flying spaghetti monster or Zeus.