I am concerned that this debt may be time barred. In Scots law a debt becomes time barred unless there is a written acknowledgement of it within five years of the date of raising court proceedings. Assuming time bar doesn't apply you can sue him for the money as the debt is what is called joint and several. Experts on JustAnswer aren't allowed to recommend specific solicitors but you can contact the Law Society of Scotland and ask them to recommend a civil court solicitor in Glasgow. www lawscot.org.uk for contact details. Happy to discuss further. I hope that helps. Please leave a positive rating so that I am creditd for my time.
He would have to instruct a solicitor to transfer the title back into joint names. If there is a mortgage in his name this might not be possible without also changing the mortgage. Is that what you mean?