Is there a California family code that states you have to file for sole custody if there was a history of domestic violence?

No, the code does not say that. The code says, in summary, that if there is a history of domestic violence, (and there is a definition of what is meant by that) then the judge, if he is hearing a contested custody case, should assume/presume that it would not be in the child(ren)'s best interest to award custody to the perpetrator.

Custody litigation is one of the most complex things I do (and I've been practicing law for 30 years); you should at least speak to an experienced family law attorney before going to court.