The EN comfort rating assumes you have an insulating pad underneath you, are sleeping in a tent, wearing a base layer and a hat, and are 25 years of age. Keep these things in mind when you do your calculations.
A few other things to consider are how comfortable do you want/need to be. As an example, I can get adequate (not great) sleep when fairly cold, so for a couple day trip I am not to worried about being 'toasty warm' on longer trips getting good sleep becomes more important.
This is an area where inexperience can rear it's ugly head as everyone is VERY different when it comes to warmth and how well they sleep. It affects not only your bag, but your ground pad. Once again, using myself as an example, I can get by sleeping on snow with a standard weight evazote pad which has a pretty low R rating (probably around 2 or so) I can't imagine EVER carrying the extra weight of a R value 9 pad. For years I winter camped with a ultralight thermarest – R value was probably around 4 or 5 at the most. Other folks would "freeze to death" with such a combination.
Maybe not super helpful to your application, but it may give you some things to think about.
It should also give you some idea of why it is so very hard for anyone to give you an accurate recommendation over the internet. Like it or not, you are going to have to get the best information you can and go with it. Doing some short trips and trying gear before you go on your big rip can be invaluable.