youngster,
I have resealed my hut once since I have had it. I just use Thompson's Water sealer.
I use this on all my wall tents and anything that is canvas. Works great !!!
I would not worry about seeing daylight (unless the one that you saw was made wrong). I will set mine up and see if I can see daylight. I know that mine has kept me warm and dry in some pretty nasty weather.
If it is cold and you run a propane heater, that puts out a lot of heat, your hut will sweat in the inside. This is one of the downsides from using propane heat. I have found that if I run my heater so I am just comfortable, the sweating does not happen.
Also make sure that you vent your shanty while running your heater.This is stuff that you might already know.Sorry if that is the case.
As I said, the Speed Shak is a tough shanty and easy to set up.
Wyo Ice