The position is that where two persons are named on the title to a property neither person can deny access to the property to the other in the absence of a Court Order to the contrary.
Similarly, the property cannot be sold without the agreement of both parties, as they would need to sign the sale contract and Land Registry transfer form. However, either party can apply to Court for an order for sale.
They overriding concern of the Court should there be any proceedings will be the welfare of the child, which is to say that they child's accommodation will be of paramount concern.
In view of his apparent denial of the situation I would suggest that you seek to arrange counseling and possibly mediation. Mediation would help to the extent that the mediator would be neutral and would help you to work out the best way forward. There is national organisation of family lawyers would can assist and direct you to mediation in your area:-
It would be best to try this avenue first because it is less expensive than instructing solicitors, but if no constructive way forward is found then you may have to instruct a family lawyer to resolve the future plans for the property.
If this is useful please kindly click accept so that I may be rewarded for my time. You will be free to ask follow up questions.