- Is なの considered as a whole (grammatical expression)?
- Or is it な ,to make 不自由 an adj, and の seperately? If 2) is the case, what does の mean here?
Here の is used in the same manner as you might こと, as a nominalizer(sp?)
It is common to end a sentence with ことだ or のだ basically turning the sentence structure into " it is the case(thing) that ..."
Effectively there is little difference in the meaning than if it was not there at all, but it can have connotations of politeness, so for instance in the sentence you have given, there is an implicit respect for the Grandmother.
This 文法 is used all over the place, and if you spend much time in conversation you may find yourself doing it without thinking.