Trigger warning! Domestic violence

Hiya 

I'm not really sure how to write this post but I need some advice and as much as I'm hoping that no one is/has been in the same/similar situation......I'm hoping that someone could help me. 

Has any parent been through the special guardianship route of their step child......in a domestic abuse setting? 

My step son is now 16 but I have been his mum for the last 5 years, I am currently fighting for a diagnosis (for the last 5 years after his father has just put his behaviour down to 'naughtiness'), I have literally done everything.....put support in place at school etc. After 4 years of mental abuse and financial abuse towards both myself and my step son, I plucked up the courage to kick him out, but have since found out lots of information from various people. Anyway....we have a family support worker and because the child has been conditioned to not get his dad into trouble with the professionals.....the support worker has said she can't do anymore with regards to investigating domestic abuse because it hasn't come from the child. This is a child who can not vocalise his feelings and does not understand emotions....she has said that unless he vocalises something she won't take it any further....despite the fact that she has seen first hand the impact contact with his father does to him. How can I explain to him that what his father is doing to him (not physically but mentally and financially) is wrong and he needs to speak up and say it. There must be a way that professionals can see and understand that there is abuse happening without the child actually vocalising it if they are unable to?????