Electrical Jack problems of the 2005 Toyota Scion Tc

I bought a 2005 scion xa on November 15, 2004. On December 20, 2004 the driver side front tire blew out, after hitting a bump in the road. The tire had 3,966 miles on it. The side wall blew . As we my children and I processed to change the tire. The jack slide sideways, causing the car to fall. It hurt my 15 year old sons hand, if I hadnt shoved my tire under the body of the car and screamed at him, the car would have landed on him and his leg. We rejacked the car back up and the jack started sliding again. We were in a level gas station paved parking lot. The third time we jacked the car up the jack started slipping again. I believe these jacks are dangerous!! the side wall of the tire is also too thin. I had to replace the tire. I will buy a new jack to put in my car. I would like someone to check into this matter. Also the manufacure stated the car would get 32 mph city, 38 highway. We are getting 28 city and 31 on highway. This is my first new car, I am not impressed! I am very disappointed in Toyota, we have had Toyota's in the past and I got better milage out of them.