If the boot doesn't fit your foot, there is no reason to buy it. I love them and think they are the best, but you would be miserable every day wearing them. It is possible you could correct the feel of the boot with a different insole. That may or may not work.
We also sell the FXR line of boots. They are what they are. They are comfortable, but most people need to replace them each season. Not much support. They should be waterproof, but if your feet sweat you will probably still feel wet. You will likely experience that with any non Gore-Tex boot though. I don't really know how else to explain them. They are an average snowmobile boot. Not the best, but not the worst either. Sorry I'm not more help.
You may also look into Trukke and HMK. Many people find those to be comfortable as well. If you like the HMK, just don't get something rated to -50as your feet will be sweating constantly and will end up cold from being wet.