Let him have his lies.
My XP (split in 2006) did exactly the same. Disappeared for 9 months, told his family and friends loads of lies about me, was warned by the police about harassment so stopped and then started legal proceedings for contact.
I was seeing women's aid and so I went to the MIAM and they said mediation was not appropriate because of the abuse. It went to court.
He was also a master manipulator. I was terrified. He initially got supervised contact building to unsupervised but when it got to there he kept breaking the contact arrangements even though I had let him pick the day time and place. New orders kept being made, he kept telling loads of lies in court, I worried he was being believed.
Eventually after a number of years the judge ruled that he was a liar and had brought the suit vexatiously, dismissed it saying I had never obstructed contact and ordered him to apologise for 'saying the worst things you could say about any woman, never mind the mother of your children'.
It was unexpected as the whole way through there was no indication of the impression the judge was getting. I was vindicated in the end, though angry at all he had put us through.
So my advice is to be calm, reasonable, honest and firm and ride it out. Let him make himself look like the ridiculous and vengeful liar he is by not reacting.