Well first of all, sweating isn't the key to lose fat, but your program looks quite nice and I suppose that you are making progress.
However the most important thing is that you get a good diet. When you are at 250lbs and want to lose fat you can't afford many burgers or chips. Chicken, lots of vegtabels and fruits will be a good start.
I saw a documentary yesterday about a boy (think he was around 300lbs) who worked out everyday, after the workout he went out and bought coke and roasted potatoes. In 2 week he had put on 10lbs more.
Anyway keep up the good work and good luck
