Get proper advice from a solicitor.
Literally my first sentence of the post you quote.
I'll expand what I wrote:
Make detailed notes before the appointment, including any questions you may want to ask.
At your first appointment, give the solicitor all relevant documents, and a clear description of what has happened. Ask them what your options are.
Consider your options, while knowing your own truth. Know what you think is fair. How else can you decide what you want to do next? Not taking it any further is, of course, one of your options. Never make a decision without thinking about it for at least 3 days.
Consult solicitor, and either instruct solicitor to act, or ask them for the bill.
What happens after that depends on what you instruct the solicitor to do.
This is the exact strategy I used in 2011-12 when divorcing my abusive Ex (thankfully no violence involved). I was supported by an army of women on the Relationships board, to whom I shall be forever thankful.
One last paragraph: don't let your step-father yank your rope or press your buttons. Just try and remember exactly what he says, which can be revealing as to what he might be thinking. Anything he suggests re solutions to the house, write down the details, and say "I'll have a think about that.". Keep your own cards close to your chest, and don't let him wind you up. Grey rock.