you might need to search online for the average cost in CA

Usually, there is a guidance for average child expense. For example, check this site

http://www.babycenter.com/cost-of-raising-child-calculator

Its number is $19000 per year. It will be much better if you can get a CA estimate. I think that 1000-1500 per month is very reasonable in US.

http://en.wikipedia.org/wiki/Cost_of_raising_a_child

However, California is very expensive. So you might get a higher number. You can ask your husband/lawyer for his number too if you do not have a lot of time. According to your original post, your cost is 1100, which I think your husband will very likely accept.