Yes it is more efficient to heat the kitchen with a range instead of a
furnace. The range is 100% efficient. all the heat goes inside the
However, heat distribution will be uneven, the kitchen will be warm
when the rest of the house is cold
The gas flame produces two primary products of combustion, carbon
dioxide and water vapor. Both can cause problems in large enough
It also produces some carbon monoxide.
I would like to ask how you like living inside a chimney??
For ocasional use, the stove is fine. It depends on your climate. But
if you use it for only heat source, you may make humidity high enough
to cause condensation on windows and window sills, which could promote
mold. You will increase the CO and CO2 levels in the house as well as
depletw oxygen levels. It depends on how loose your house construction
is and how big your burners are, as well as the size of your house.
No simple answeres here without more information.
Ask Nick Pine, he loves doing supposing and calculations.