In some religions god doesn't have a name. So, to label it god even for the sake of conversation would be wrong or incomplete. Which would then make the term life-force or god useless labels if it can't be described and defined.
No. I don't agree with this. As the Zen master said after Enlightenment, "You have to say something". Yes, while it cannot be defined or named or talked about, you have to say something if you are attempting to describe, point to, or otherwise communicate something about it to another. The mind requires that, it thinks in words, even if it is not the mind with which you apprehend that which cannot be named. The mind is meant to look beyond thinking about it, though the words themselves.
The problem is that people take a metaphor and interpret that with the mind as a descriptor of what it is, putting a boundary around it, like naming something a dog or a cat, or a tree or a rock. If the mind mistakes the finger pointing at the moon with the moon itself, then the mind is mistaken. But it is not wrong for someone to point. "You have to say something". The mind looks at the words, and then uses them to leap off into realization beyond the words. Think of them like a diving board.
Since god doesn't have a definition, it is (how to say) just as meaningless to talk about it.
That is why we use metaphors and mythologies. They are the equivalent of the dance. But to ask to explain the dance, misses the point of the dance. To ask someone to define God, misses the point of using the word God.
1. How does a person talk about god when its only a label for something he or she cannot define?
How does a person dance or sing, about something they cannot define with words? Is life only about the mind and its thoughts, or about the whole person? Isn't this what true art is all about? To express the inexpressible?
2. How does one know he or she experiences god, when that person cannot define what he or she has experienced?
When it is beyond description, that's the first clue.
3. What's the value of an empty label?
What is the value of poetry? Do you ask a poet for a critical analysis of his poem, in order for it to be heard by your soul? I would think that would indicate someone is stuck in thinking about life, as opposed to living it with their whole being. Something is missing. The whole person isn't present.