Jane,
You have an amazing attitude! What you and your family are going through is not easy but you seem to have a great grasp of the situation. It can be overwhelming trying to digest all of the medical jargon on top of coming to terms with what is happening to your mom. You seem to be doing everything you can to make sure your mom is getting the best medical care, is comfortable, and well cared for. I am so sorry you have to be here, but this forum has been a godsend for me and many others so I think you are in the right place. I wish I had found it before my mom passed away last month... you are in good hands.
Speaking as a former caregiver, you are making the right move by not having your mom endure radiation. It is not kind, and I can't imagine someone 25 years older than my mom going through it... it certainly takes a toll and if it is going to decrease quality of life, it is not worth it in my opinion. It sounds like your mom has a great handle on both the physicaly and emotional aspects of what she is experiencing... and while I know some days you may seem to be at peace with it, there will certainly be days where you are not. It is against every fiber of our beings to let go of all control and allow nature (or science) to take it's course. But in these situations there is very little we can control.
Best of luck to you and your family, and good health and peace to your mom. Hang in there and take care of yourself while taking care of your mom. Give her all the love in the world, I know you are. And everything will be ok.