Try your local women's aid if you are having problems getting through on the helpline (0808 2000 247 - it is better to call the helpline at night (7am-7pm) as lines are busy during the day. But you may not be able to do that, hence try local).
Do have a look at the Womens Aid website - lots of useful information. Eg covering your digital tracks, as mentioned by a pp.
the law is the law, regardless who has what lawyers. Marital assets are divided re guidelines. Is he self-employed?
You may need a lawyer who is experienced in domestic abuse - Womens Aid will have a list of appropriate lawyers in your area - because I'm not sure the advice to stay at home to ensure you get custody is sound advice (especially for your career!). You have been the primary carer so far which should ensure you get custody. Women's Aid can guide you on this.
At some point (soon!) do the Freedom Programme - essential for those experiencing domestic abuse. It is a wonderful course, I can't recommend it highly enough. Find a course near you
You can do this. Plenty of us have - including me (when I never thought I could. He also had a team (ffs!) of hotshot central London lawyers: made no difference).
Women's Aid will help you 'get your ducks in a row' (financially, practically, emotionally) before you leave safely.
DO NOT TELL HIM YOU ARE LEAVING.
Good luck. One step at a time 