I don't know how useful I can be to you, but I'll try.
I have read your previous threads, including the one by your STBXH (Here on in to be referred to as "The Arsehole"!)
Sometimes I find doing something practical helps to make you feel in control.
Firstly, I know you have depression, which is being successfully treated. Make sure you stay in control of that, with the right level of medication.
Make sure you have a school allocated for DD by the LA where you are currently living. Were you intending to send her privately? If so, still do the above, but also speak to the private school about bursaries.
Buy the absolute minimum you can of uniforms. Remember, these can be refunded if they are not washed, named or emboidered yet, so obviously hold fire on those things.
If you do need to move, you can change schools, then, but cross that bridge when you come to it.
Why will moving out of London be best for a City lawyer? Or would you look at some other kind of law?
I don't need to tell you to keep looking for jobs, getting your CV out to all the agencies etc. Any positive and practical activity will help you feel in control.
As will rallying your RL friends to give you whatever support they can (financial, emotional, practical....)
I know its all up in the air, but you are not a failure. Remember, bad things happen to good people!