You need to look to your divorce decree for the answer to this question. Does it require that you remove his name from the property? If so, he may be able to get a judge to allow the sale of the house. If there is no such provision, then it is unlikely that any judge would require the sale. My guess is that the Decree does not require the sale and that's why his threats have been "subtle" instead of his telling you what his rights are and proceeding to exercise them.
This answer does not constitute legal advice and does not and is not intended to create an attorney-client relationship. The law may vary depending on the state in which you reside. It is intended only to give some direction in which to seek assistance.