
1. For that matter, the Amazons may simply have a different military grade as well. After all, a naval captain is not the same thing as an army captain. So, if the Amazons use ranks like Warrior, Scout, etc. then Captain may be all they need. And for that matter, they may also have different grades of Captain. Captain of the Guard is the royal guard...there may be an Aerie Captain (okay, a bad term for nesting grounds of the grypohns, etc.)
2. I don't mind ideas of half-races (if one wants to use the term), but one must be careful not to go to far. I've had players go, 'Well, I'm quarterling elf, 1/8th orc," etc.
3. I actually assumed there were some small villages, if for no other reason than to raise the crops Amazons would obviously need to live. They don't actually engage in any external trade, but they do rely on slave labor. One could almost foresee a plantation system with Amazon overseers and guards.
However, if you don't want to have villages, you could also assume the Amazons mastered terrace farming (look at the Incans) to help provide the foodstuffs they need.