The higher temp should help combat what may be causing the illness (and speed lifecycles up), and it may also help boost the fish's immunity (like fevers can be good for us).

If you don't have a heater to put in with him, then if you could put him somewhere in your home that is warmer (ie. not against an outside wall, near a light, wrapping a towel around the tank).

I would use both MII and the epsom salts (as per the directions in the dropsy article) at this point.

~Ash