What do your court orders say about the father's visitation? If he has court ordered visitation, then you are in contempt of court. If not, then his taking you back to court will surely result in the court setting down visitation formally.

You made a big mistake and will lose on this issue unless you have extremely compelling evidence of direct physical harm to the son, such as hospital reports showing treatment of his abuse, or direct testimony by a therapist or guardian ad litem.

If you are found to have been obstructive to his visitation, it is possible that you may be responsible for his legal fees on the issue as well as your own.

Child support is a completely separate issue from visitation. You said "He has done nothing for our son for 8 years"

Does this mean he has paid no child support for 8 years? That he hasn't been in the child's life?

The amount of child support will be set by the evidence submitted to the court. If you believe he will lie and submit false evidence about his income, simply saying so will bear no weight. You are very unlikely to be able to subpoena records yourself, you need a lawyer.

For an estimation of what child support might be, see:
http://www.childsup.ca.gov/resources/calculatechildsupport.aspx

What event happened that caused you to deny him visitation?