legal rights to percentage of house value

22 years ago I bought a house with my then partner, and my existing house which I owned completely by myself was taken by the builder who was selling the property we were bying as 50% deposit.I didn''t sign anything at the time, but have now been told I could claim 75% of the existing house value, which is on the market at the moment....is this correct? Also, as my ex is rather violent towards me and is resisting selling the house to the extreme, could I buy him out instead by giving him a quarter share of the selling value? (I would be struggling to give him half)
The house has been on the market for 3 years now and has had 25 requests for viewing, but as he is living there and I''m not, he is always out when they turn up, so no viewing have ever happened. I am now so fed up with the situation that I am trying to take over the viewing myself, but, he has had the locks changed etc. I have managed to get a part set of keys by keep turning up and helping myself whilst he is ranting and swearing at me. Also on one occasion he called the police and threatened to shoot me, he does have a shotgun and the police came very quickly and took it off him, although he has it back now.
I am desperate to put an end to this and get the house either sold, or him bought out.
There are no children involved.
I would appreciate any advice please.

Not sure about the first part the not signing and claiming 75%, or who even suggested this.

Anyway yes you can buy him out if he agrees, in fact you can both agree just about anything you like as long as you have it written as a Consent Order.

If he wont agree then your left with court, it takes a long time and can cost an arm and a leg but it is the only option for some.

You say partner not husband. Are/were you married?

We lived together for 22 years but never married. I was married previously which ended amicably, and is how I came to owm my own house, as we sold the joint property and split 50-50 without any lawyers involved.
I now feel like I''m losing this to my present ex partner.
He will never agree to split anything or move out as he wants to stay in the house, but without my presence spoiling it for him.(he;s retired, but I still work full time.
My next concern is...if I do manage to get a byer for the house, can he refuse to sign, and what would I do then?

If he refuses to sell then you will need to apply to court. Since you are not married this will be a civil case rather than a family one. The law is a lot more straightforward, chances are if the house is jointly owned then you''ll get 50% each after mortgage and sales fees are paid. It doesn''t really matter where the money came from, if the house is jointly owned and there is no deed of trust specifying a division other than 50/50, then it is owned 50/50.

If one of you wants to buy the other out, then it''s much easier, they should be paying the same amount of money that the other would have got if the house were to be sold to a stranger. That is the value, minus mortgage, minus potential sales fees etc, divided by 2. But obviously one buying the other out requires cooperation and agreement of both parties.