I can tell you by spoonfuls, to give you an idea of the proportion... Two spoonfuls of cream cheese and two spoonfuls of pumpkin. About a tablespoon of butter. I'd suggest doing the Splenda and pumpkin pie spice to taste... I just sprinkled some from the box, didn't actually measure it. Play with it until you get it just right.
It's amazing how delicious full-fat foods are with low sugar... Low-fat stuff with higher sugar never satisfied me so much!