It sounds like you have a lot of different, very specific ideas about what these words mean. I was speaking more generally, and suggesting that all of these terms are roughly synonymous. But you ask some really interesting questions. I'll give it some more thought, but I'll share my initial reaction.
If you're not fighting, then you're not in a position to evaluate whether the person can fight. They may have fighting spirit/gameness/toughness. They may have technical ability. They may have physical traits that lend themselves to fighting.
But if they aren't fighting, whether by choice or not, they just simply aren't fighting, and so you can't evaluate whether or not they CAN fight. So, maybe?
The best example I can think of to illustrate this is a few years ago, I read a news article about a person who was training for the American Ninja Warrior competition. She was attacked, and if I remember correctly, the bad guy had a knife to her throat and attempted to sexually assault her. She fought back and kicked the dude's ***, and then ran away. She had no formal martial training.
So, in this example, I'd say her physical strength and overall fitness combined with her fighting spirit demonstrated pretty clearly that she could fight.
Could be that you don't, and if so, then I'd say if you're in a situation where you need to fight, you would have to rely more heavily on your technique and your physical traits (strength, athleticism, etc).
Makes sense, I guess. I'm not sure how you're defining fighting spirit, but I don't think it means the same thing to you as it does to me.
had someone try this with me talking about Chinese martial arts in an empty bar.. asking what would I do 
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