Secondly, the calls for assistance is basically reports to the police, and they (8 per 1000 in Kentucky and 5 per 1000 in California [ACS 2008 estimate]) are close to the divorce rate in the respective states (13 per 1000 in Kentucky and 8 per 1000 in California). Overestimating by saying that all divorces are settled in court (some numbers say that ~ 4 % are), the 60% of cases involving domestic violence means that there would be 7.8 per 1000 domestic violence divorce cases. As this is the same amount as the number of calls for police assistance (8 per 1000), your claim that the rate of domestic violence reported is orders of magnitude greater in court is pure falsehood. The case in California is even worse, with estimated 3.2 per 1000 domestic violence cases versus 5 per 1000 calls about domestic violence.
https://www.census.gov/hhes/socdemo/marriage/data/acs/Evalua...
Using the number "Domestic Violence-Related Calls for Assistance" as reference on how to scale from Kentucky to California, ~60 % of divorce cases will have no mention of violence.
(In 2004 Kentucky had 800 calls per 100 000 inhabitants and California had 500; the assumption is that number of allegations in hearings scale with the calls of assistance).
https://aifs.gov.au/publications/allegations-family-violence...
https://oag.ca.gov/crime/cjsc/stats/domestic-violence
http://www.ncdsv.org/fortcampbell/I-12_Kentucky%20DV%20Facts...
http://www.census.gov/popest/data/state/totals/2004/tables/N...