I am going to answer your questions one at a time. 

For either black raspberries or red raspberries: My family prefers seedless. I typically process my jams by weight (230-235 gr per cup). Black raspberries ratio is 5 cups fruit to 7 cups sugar. If I remove all the seeds, should I increase the amount of fruit to 5 cups?

Answer: If the recipe says 5 cups fruit or juice then yes you will use that same amount with or without the seeds.

Do the seeds add anything to the jam?  Answer: No, the seeds are really optional.

Nutrients? Seeds add no nutritional value. 

Pectin? they do not add to the pectin.  Do they just take up space? They just take up space.

Alternatively, with all of the seeds removed, would you recommend using the jelly ratios, even though all of the fruit pulp remains? Answer: If you strain the berries and have juice then use the jelly recipe. If you are squishing the berries then be careful to not squish the seeds through, if there is a lot of pulp then use the jam recipe. 

So, over all the seeds can safely be removed. Jelly is using the juice, Jam has fruit. 

If you have more questions, please contact me. Karen Fifield, Food Safety Educator, <personal data hidden>

Have a great day!