Good afternoon Leah,
As the father is still out there, there are only two ways that the California court will grant you a change of name for your minor son. And, I'm afraid that the restraining order which held that you were the custodial parent
is not of any use in this situation.
1. You will have to get the father to sign a document to be filed with the court agreeing to the name change. And if that is not possible for you to accomplish, then,
2. You will have to file a Petition for Termination of Parental rights
in court, and get an order form the court finding it in the best interests of your child that the father's parental rights be terminated.
The father's parental rights can be terminated without his consent if the court finds that his continuing relationship is not in the child's best interest. This is typically shown by a complete failure of the father to maintain contact with the child over a period of years along with the failure to pay support during that time.
While the failure of contact and support may support the termination of parental rights after just a year, the fact that there has been no contact, and presumably no support in that time either, makes it very likely that you will win this argument and be granter the Order of termination of the father's parental rights.
As soon as that is done, you may file your Petition for Change of Name for your child in the court, and the court will grant the petition.
You may reply back to me again, using the Reply to Expert link, if you have additional questions.
I wish you the best in your future,