I would go to the local Child Support Enforcement Agency and file a cliam against him for the support. Maybe he will start paying as he should if he is ordered by the DA themselves. I would also seek the advice of an attorney, but also think about the consequences of all actions taken, this could be a blessing for your child to finally get the money he/she deserves or the father may retaliate in some way - so be careful. I also agree with Legal Beagle, get that amount raised, this is not the 1900's anymore!
Good luck,
Ukiah
------------------
All that you have read in no way is Legal Advice, it is a matter of opinion to help you in your quest