Alexandra, salamanders do not need artificial heat sources from their keepers. They will tolerate temperature just above freezing to mid 70's. You have to worry more about extreme temperatures, freezing and high 70's into 80's. Another concern is drying out. Wintertime humidity is low, so your setups can dry out faster. Winter time is the easiest time to keep most caudates, because the average room temperature will drop to 60's to low 70's. Unless you live in my grandparents house who blast their wood stove all winter keeping the indoor temps around 80!
Even in their home, there are rooms that are much cooler (back bedrooms, storage closets, etc).
If you are trying to breed salamanders from cooler regions, they will need a cooling period. Depending on the species of salamander, this temperature can vary from 40's to 50's.
Breeders have even resorted to keep them in the refridge for a couple of weeks.
Feeding salamanders through the winter is fine. If your are dropping the temperatures really low to stimulate breeding, (38-48F) they may not feed or feed very little due to the slowing down of their metabolism. It has been reported of a naturalist observing Red Spotted newts below the ice on a frozen pond, foraging for what he thought was food! I'm not sure of this account, but have witnessed newts and salamanders mating in ponds that were partially frozen.
I would recommend researching your salamander's natural history or habitat in the wild. The challenge is trying to duplicate that in an enclosed setup at room temperature.