Shriek - so sorry to hear you're having a bad day. It's horrible to think of your child stepping on eggshells around him, we all know how that feels. I don't know what the answer is, but it sounds like you'll need to speak to someone - better for you to do it yourself, contacting who you want and getting things rolling on your own terms, than having it foist upon you if he decides to try and get PR by going through the courts. Stay strong.
MrsOP - oooooooh yes, the FW who thinks it's ok to snoop on us (but lord help us if we suggest he isn't trustworthy). In the end, before I left, I became a dribbling ball of paranoia. I hid the Lundy book somewhere different every few weeks. I deleted all my texts as soon as I'd read them or sent them. I started using incognito browsing and using the onscreen keyboard to log into anything (as I was convinced he had key logging software on my laptop). I also found myself refusing to have conversations about him in the house (eg with my mum) and standing on chairs to look in light fittings as I was sure the place was bugged. Some of this may have been my shattered mental state, but he liked to suggest/hint that he was 'listening' or knew what I'd said to so-and-so in an email, so it wasn't all just me. Do all you can to keep yourself safe and keep what's private private.
MrsOP, that's exactly the reaction he was banking on - he therefore gets away with not doing what he'd promised, and there is no comeback. There was a scenario in Lundy about just that, about a man creating an argument and storming off on the night he was due to do the dishes, and no-one dared call him for it, or ever reminded him to do them again - it's win-win for him. It's all part of the abuse. I was the same, I often likened myself to a rabbit - my brain would shut down and I couldn't think of anything to say, and I'd end up apologising just to stop the argument. It's not good. Your sister has never been there, so she doesn't know, it's no her fault (although she could perhaps be a little more empathetic?).
So, hilde and fingers - I think it's the funny farm for all of us (our FWs all think we are the ones that are truly mad, after all), maybe they could build us a big wing with a daily diet of chocolate and wine, as long as we were there without FWs it would be heaven! 
Hilde, am 
that he dares say 'I have never once deliberately set out to make her feel worthless, inferior or to hurt her'. I think that's an out-and-out lie. I know they don't go around thinking 'tomorrow I'll hurt her' or 'tomorrow I'll put her down and really make her feel bad', but it's a choice they make in that instant. It's still a choice. He's still not seeing it. Does he think he accidentally called you horrible names and woops, tripped over and assaulted you by mistake? Now, if his response to your dad had been something like: you are completely right, I am utterly ashamed of myself, I've done some truly awful things and put hilde and the kids through hell. I'm trying to get myself back o the right track, hopefully hilde will still be there for me at the end but if she's not I'll understand, she's a fantastic and strong woman.... but he's still whinging about himself. That's all I hear - me, me, me (how many times does he use 'I'???). And hilde needs to see someone too, cause obviously she's the one who's actually bonkers. How bloody blinking dare he!!!!! I am increasingly irate on your behalf hilde, to the point where I am laughing at how angry I am! I don't often get angry! [anger] I may turn green any moment. 
Oh dear, I have...
Sorry for the rant, I had to get all that out! Have you heard from his programme at all, had any updates or anything? Maybe it would be worth taking him up on the offer for the older kids to talk to someone and get out what they are feeling?