Dianne is right about that - anyone can file the paperwork.
Just so you know, the Plaintiff in a divorce case in California is referred to as the Petitioner. The other party is referred to as the Respondent.
Best of luck.
I agree with David. You should pay for a consultation with an attorney in your area - just to get the forms straight. Here's a blog article I wrote on the paperwork process, but it's probably not as detailed as you're going to need:
I agree with John. This may end up being quite simple for you. Because you were together for such a short time, you may qualify for a Summary Dissolution. Below are links to several articles that may be useful for you. Good luck and I hope these help:
I agree with Martha's response. It sounds like you are fairly well educated on the topic, but we have a brief explanation of the differences between legal and physical custody in California on our website. Here's a link for your convenience: