Is that 1 teaspoon of concentrated stevia, powder?
Is that 1 teaspoon of Agave syrup also?
What fruits have you done?
What fruits require lemon juice and how much?
If I have just two or three fruits I can do that would be great.
I use about a teaspoon of concentrated stevia & then add agave to taste, anywhere from 1/2 to 2 cups. I add it about a half cup at a time until it tastes right. A lot depends on the sweetness of the fruit & how sweet you like your jam/jelly. I've found out that folks in my area like really sweet, so I generally add a lot.
I've done the following sugar free: Strawberry Jam, Blueberry Jam, Fig Preserves, Kiwi Jam, Plum Jam, Muscadine (grape) Jelly.
The instructions I have say that these fruits need a little lemon: blueberry, raspberry, apricots, sweet cherries, peach, pear & plum. 2 tablespoons per 4 cups of fruit/juice.
I purchase my pectin in bulk from Pacific Pectin. These are from the instructions they sent with their LM-0, sugar-free pectin. I like it better than the store bought pectin and even pomona.