It is completely up to your carrier to provide updates. Google gives the new updates to the carrier, who then customize and make it work with their network.
Dont use the app killer, thats probably causing your problems. You dont need it, Android will kill apps when it needs the memory. Dont root, it voids your warranty. The only thing you can do is take it back to your carrier and ask for a new phone. Unfortunately, since you went with a local carrier, you may not have any opportunity to complain to higher up people. Just looking at their website, its horribly designed, and they completely lie about their coverage area. They only cover a small portion of South Dakota, and thats it. Good luck paying roaming fees when you leave the state.
Thats up to you. You should have a 30 day return policy. If you are not satisfied with how the phone is performing, you have the right to ask for a new replacement phone, or just return it for another model.