Im with @Barry on this. Not unless you race your car.. you do not change the circulation of the watercooling system of your car. cabin heater is connected to the your car's engine cooling system. try turning on the heater when your car overheats.. this will gradually cool your engine, not 100% to normal temp but this will help you get to the nearest garage. in my experience, a car over 100k (or almost) need to change waterpump and thermostat especially here in the middle east.
I think the simple thing is to do process of elimination. do the 100k maintenance (timing belt kit. water pump, thermostat, radiator cap), while you are at it, change all the hose (all the hose!!). see if your car still overheats. for the bad smell, go to fastfit, they can clean your a/c(change gas, humidify the cabin).