Hello, Conan, and welcome to Hex Games! I already like you because you bought Rocket Jocks

Golly, another European fan. It always gives me a thrill when someone overseas gives us a shout.
Anyway, let me see if I can answer any questions for you. If I make a mistake, I'm sure Steve and Leighton will jump to correct me.
1) You'll not that it says do it once, then do it "four more" times. There's your total of five.
2) The "half-Word" rule is for when a character tries to do something that he should need some sort of training for (lock picking, guitar playing, brain surgery) but doesn't. For actions that anyone should have a reasonable chance at doing, use the full value of the Word.
In the example, the GM apparently decided that bluffing his way past a cultist is something that didn't require any special skill and let Luke use his full Nerve.
3) With QAGS, you don't look at the margin between what you rolled and the target number. You look at the actual number you rolled on the die. You want to roll as high as you can without going over the relevant number (the "Price is Right Principle").
If you have a Number of 13, a roll of 12 is better than a roll of 3. A roll of 13 is an extra-cool Lucky Break!
In you combat example, the defender would win because his roll of 10 beat the attacker's roll of 3. The margin between their actual roll and their Numbers is irrelevant. You would, however, use the difference between their actual rolls to determine damage.
So let me repeat that: always use the number you roll, not the difference between the roll and the Number you're rolling against.