sorry you are having this hassle essbee - I know how stressful this all is from experience - my ex was violent many times, though not intentionally to the children (my dd got hit by accident because she was in the way of me). We are just getting to the financial part of the divorce. It is a nightmare although ex and I are trying to be amicable - also going through the court to negotiate this can cost up to £8000 I was told, so to be avoided if possible! If mediation has failed, go back to your solicitor asap for more advice.
Btw I was told that having an SN child doesn't necessarily help with the financial settlement - my solicitor says it is the immediate rehousing which is taken into account. Also the fact that he was violent is not relevant to the financial decision - unbelievable I know, but that's what she said .
Hope this works out for the best for you soon.