Wow... good luck with the pectin. 2 things I've learned.
1.) After you strain it out of the pulp to make the 'juice' cook it down further... preferably by 1/2.
2.) To test the pectin to see if it will set or not, cool it in the fridge and then do 1 tsp pectin to 1 tsp rubbing alcohol. It will make an instant set lumpy gel if the pectin is viable. (Through this away when done, its posionous!)
I need to get the rest of my grapes done, but I have a bag of muscadine grapes to do. Yummmmmmmmm