I don't think it's a correct sentence at all. From the above sentence I would conclude that the guy studied hard after he passed the test. I would rather say:He passed the test because he studied hard...
I agree with you, on the grounds of the parallelism between "[He passed the test because he studied hard, was calm and .... self-confidence.
2. he had
3. because he had
What is correct?
I think that the first option is the correct one.