1. You don't have to sanitize it- it's preboil. I just clean it with a hot water rinse right after emptying the mash. If you let it sit, it's harder to clean but an oxiclean soak will clean it nicely.
2. Yes, that is a concern. That's why I finally switched over to all-stainless, but I used Igloo coolers for about 6 years, brewing twice a month. If you go over 180 degrees, they will warp and crack (as I know from experience
) and I do wonder about the plastic leaching something as they aren't designed to be used with hot water. I noticed that the first time I used it with hot water, it smelled "plastic-y" and so I poured out that water and never noticed that odor again.