Spider mites like dry plants. So keep the humidity up around your plants with a humidifier or a pebble tray. Take your plants to the shower and really hose them down and that should help with the mites. Look at a product called neem oil. It is quite safe and is an insecticide, miticide, and fungicide all in one. It is a natural product derived from the neem tree.

I only re-pot or up pot my houseplants in the Spring. At that time, they are starting to wake up from winter and put out new growth. I would only go up one size pot, such as a 5-6″ pot at this time, unless it is really rootbound and will have plenty of light to put out new growth.