Although I haven't made this actual recipe (yet), I know that my daughter used a tablespoon of Paprika for only a pound and a half of salmon (with some brown sugar, pepper, salt, and ground mustard)...and it was delicious! Chicken Paprikash calls for 3 tablespoons or more.
I think that the trick with Paprika is to make sure you use either the mild (regular) or Hot Hungarian Paprika to your liking. The mild goes a long way. Dip your moistened finger into it and taste test it...something my Mom told me to do with herbs and spices many years ago. You will know how to adjust accordingly.
For 4 and 1/2 pounds of ribs, I think 1/4 cup of paprika sounds appropriate. Most of the rub is going to come off during cooking anyway. :)
God bless Taste of Home for filling our tummies and our hearts! :)