Pumpkin: You can use fresh pureed pumpkin or canned pumpkin puree. Either one will work. Of course, fresh is always better.
Sugar: Yes, 2 cups of sugar sounds like a lot. The two main ingredients in jams are fruit and sugar, used in a 1:1 ratio. The large amount of sugar acts as a preservative allowing the jam to be stored for a longer period of time. If you reduce the sugar, expect the jam to spoil or mold sooner than the suggested storage time.
The jam will keep for up to 3 months stored in the refrigerator.
* Percent Daily Values are based on a 2000 calorie diet. Since different brands of ingredients have different nutritional information, the values shown are just an estimate.