Relax, brummie, there's no think about foster care as that is not going to be happening.
From what you've said, it seems obvious what's gone on here and the pantomime has been entirely occasioned by the demon popping up from the trap door after a considerable absence and wanting to be centre stage again.
It does sound as if your ex is away with the fairies and I urge you to be advised by your solicitor with regard to contact as whatever progress you are able to make with dd following this debacle could be rapidly undone by her df.
When you've been bullied by a dominant personality it can be frighteningly easy to slip back into a passive or downtrodden state wherein you believe that they'll always hold sway, but you've achieved so much in bringing your dc back from Oz and settling them in the UK and it's time for you to realise that you have the strength of mind to stand your ground and face the bully down.
It's not easy being a middle child and it's probable that the lure of being a 'spoilt only' has turned her head - and shame on him for behaving with so little consideration for the wellbeing of her and her siblings.
Give each of your dc a specific role in 'team brummie' and make sure your 11yo knows that she is especially valued for her position as centre forward in the middle of the wingers. What you don't want is for him to be able to influence her into scoring an own goal because I don't believe she'll have the emotional stability and security with him that she has with you and her siblings.
I find it particularly worrying that she may equate self-harming and panic attacks with gaining attention and you will need to tread carefully to avoid her using these devices to gain her own ends when it is patently not in her best interests to have her own way.
He is a nasty pernicious sod, isn't he? He may have set his 11yo dd on a most destructive path and I wonder what manner of man can be so insensitive and have so little regard for their dc?
If you have any opportunity to talk to him out of earshot of your dc, give him both barrels - and then blast him with automatic shots. The twat deserves no less and some would say he deserves considerably more.