How can I safely re-heat a chicken pie without burning the crust?
Foil is the way to go, combined with not too fierce a heat. You want to cook at about 160°C (320°F) until the centre of the pie is piping hot. To lower the chances of burning, portion the pie prior to reheating. That way the centre will get hot more quickly. 

Reheating more than once is generally not a good idea for safety reasons. You can however portion one night's pie and keep the other in the fridge.