Cleared but ex still making false accusations and spreading malicious gossip

[me15]

I am posting on behalf of a friend who is in a right mess. Hesplit form his ex in mid 2013 whom he has 2 children with. She also has a son from a previous relationship. 2 days after their split she reported him to police claiming their son and her own son had said he had been abusing them. My friend voluntarily went to the police and was interviewed but no charges were made as there was no evidence. He had to go throught the courts to establish contact and had no problems. A few months later she made a complaint bout the police statting they had not done their job and consequently socila services and CPS became and my friend was intervewed again along with the ex's son from a previous relationship. The boy's interview found he had possibly beed 'coached' to say things and that it made no sense and he used 'adult' language. No charges were made against my friend and social services and CPS were more than satisfied and happy for him to continue with contact and overnight stays with his children. Things carried on normally for a further few months until the ex made another complaint about him to police and said he if wanted to see the kids he would have to take her to court again. He has now not seen his kids for 7 months as he cannot afford legal fees, he is still paying off the fees from before and she has been putting stuff on the internet about him being a peadophile and spreading things through mutual friends. The police know she is lying but they say they can't do anything about it. He is so depressed and in a bad place. She said before they broke up she was sick of taking him back everytime they split up and that next time she would do something to make sure their relationship was over for good. This is what she did. Her uncle and cousin are both convicted child abusers who abused her other cousin and she consequently got a large pay out in compo. It seems a bit of a coincidence why she choose this path to go down. Please help us as we are afraid he's going to do something stupid.