My x-gf lied about our seperation date to collect more child support what are my options?

After 18 months of an ongoing court custody battle fighting for custody of my 1 1/2 yr old son ( As I am the father & initiated the Custody Case) the mother falsified all income & expenses on the financial affidavit as well as the date our seperation took place. I have been a single father for 8 yrs now as my 10 yr olds mother left after our divorce & has never called since, no support , Fla DOR ordered & $15K behind. The mother of my youngest claimed to have left 8 months prior than the actual seperation & the judge granted it in the final judgement. I do pay my child support for my youngest , but have a serious problem with paying almost $5000 in back support that is not even true. What can I do about this, as an appeal with the judge in my case is out of the question. He is 100% against fathers & the appeal would go before the same judge. DCF has been involved 6 times, noted ligature marks around my sons neck in a DCF case summary that I am in possesion of & also photo documented by investigator but yet my son remains with the mother. Yes I had a lawyer that I could afford at the time of my Custody case, but now my son has become a victim of the system. A lying mother, an mother ignoring the needs of my son, and abuse. What options as a single dad do I have left?? State agencies wont remove the child, judge sided with the mother (and all of this is documented very well for those who choose to doubt my claim)