He could take off with DD4, as that's how he got DD3, although he stands to lose out a lot more if he does that. He's already been told if he does, there will be a section 37 review (to place the kids in foster care) and they'll give him a penal sentance which means going to prison. He was categorically told that by the judge.
He could lie and maybe pull it off again - I wouldn't put it passed him - but I personally don't think he'd take the risk.
Of course there is an underlying fear there which I know he likes to play on, and I watch his behaviour carefully to find traits of it - for instance, threatening me take me to court, that is a trait similar to when he snatched DD3, so I cut him off and tell him I will cancel his visitation if he threatens me. He *usually* apologises when he's done that, but he seems to need constant reminding to talk to me respectfully and he frequently talks down to me, jokes about me without even realising and then needs cautioning by me that that isn't the way to behave. I get so fed up of his apologies, its like training a toddler.
On the times like now when he's just way over the top, I just go completely dark, as there's no way to deal with that level of disrespect.
I AM scared of him, but I can choose to live in fear or I can get on with my life with DD4 in the best way I can for the circumstances.
He uses court or threat of it as a beating stick and the children are weapons to degrade/criticize me so I just have to distance as much as I can, get on with life and try not to let loneliness get to me too much, which is the hardest thing.