I would get as much audio evidence as possible or other evidence. Does he hit you ?
As the child is British - and also possibly this might be classed as domestic violence - you could have options to stay in the UK if you wanted to, so his threats of using the visa could be useless.
Domestic violence
http://uklgig.org.uk/?page_id=87
I would try your local law centre first give them a call, as you probably would see a solicitor there, or if not maybe CAB. who could give you better advice and what rights you have.
http://www.lawcentres.org.uk/about-l...alphabetically
Good luck