Strange Case, Father needs info

[mystic]

I will do my darndest to keep this short.
Background 7 year old child was concieved, during a short fling.
Father has a couple of visits and support is set by the state at hardship min..
Mother moves across the US remarries and has another child, father speaks to child once or twice during the next 5 years.
But both parties recognise that the child has a family that includes Step father and new sibling, and has really never known biological father.
Then florida removes children from the home, mother tells florida she doesn not know who father is, he is never notified.
(finds out later from bio mom, because she is afraid ths state would notify Biodad)
He is still paying support to original state.
Mother and Step father then get kids back and move to CA.
Now they are recieving welfare and the state of California is going after Biological father for more support.
Father is a unempoyed student with no resources, What can he do??