Scottish Law Questions? Ask a Scots Lawyer
You can raise an action for division and sale of the property in Dumfries Sheriff Court. You'll have to use different solicitors from those acting in the estate. You will not be able to run such an action yourself unless you are experienced in civil litigation. However if I were you I would offer to have the house valued by a valued agreed by all parties and they have to pay you a third of that value. Happy to discuss further.
Unfortunately experts on JustAnswer can't take on cases personally. It's against the rules of the site. You should engage a litigation solicitor in the Dumfries area. You can use the find a solicitor tool at www.lawscot.org.uk to find someone suitable.