It is probably too hot. I have owned two ball pythins for about 10 years but I am not a profesional by no means. My experience with my snakes was the same, I started putting a t-shirt around the heating pad and realized it got really warm. I decided to buy the heating pads that people use for shoulder pain. You can regulate the T on these and I realized that they liked the minimum setting which I though was not warm enough. I never used a lamp so I cannot help you on this.
The other tip is that the hiding be half on the pad and half off that way the snake can choose and still be hiding