Well, my sales dosen't either, so I may not be the correct person to give you advise. However. You have allot of similar models with different texture. When you get more different things in your shop, sales could get better. But don't invest more time on furniture, that category is already way too overcrowded. The chances for making money there is small.
Another thing. You could put up the prizes a bit easily. This one fx is worth more than 3$ :https://www.cgtrader.com/3d-models/exterior/house/stylized-medieval-house-5dae710d-89f9-4d73-aefa-7b824224083c