I thought I'd give a sort of happy ending to all of this.
My DD and DW are getting along far better, and the worrying mean streak in both of them has gone completely - huge sigh of relief
Added to which - I've dropped out of the complex new role at work which was occupying so much of my time. I haven't resigned from work or lost any pay, I just changed to something less stressful. I 'm taking a week off work to spend some time with both of my DD's (no holiday this year so I have annual leave to use up). I'm hoping to move my teen DD to a different school which should foster her athletic interests more than i can. It's also the beginning of potty training for my little DD who has finally recovered from non-threatening but persistent medical complaint.
Life goes on and we're looking forward to the future.