Great idea! My experience:
1) I haven't (yet..Doug) had problems with my FoodSaver, so I'll keep using it for a while.
2) I fill a foodsaver bag, freeze it, make a single seal, and have used it both for water storage/transport and as a cheap refillable ice pack for years. The bags have held up under moderate abuse (in a cooler with various adult beverages) and have not leaked.
3) The bags can be dropped into boiling water (dirty water) and brought up to a good boil. To do this you must allow air space in the bag, so I don't even really draw a vacuum. I just seal them. Alternatively you need to pierce the vacuum before boiling. When I do this, I use a clamp to hold the pierced top of the bag above the "dirty" water level in the pot. I will say that I've never lab-tested the purity of the output. But I've never gotten sick.
4) I stock a pretty good supply of these in an "earthquake" locker I have outside my home... in the elements. No leaks after 2 years in the elements, but we don't get many bad freeze-thaw cycles here.