Good posts here and a lot of good in CWL's post.
Amongst the hunters, I would want to know which are successful bow hunters and riflemen. They would be better at shot selection.
I would want to know the skills and capabilities of the 500 vets. That is not a very big vet pool and with bad luck you won't have riflemen, sappers, EOD etc. With good luck, some of them will be the real deal and the rest will be obedient workers.
If the intel re the opposing force's strength and strengths is correct, this should not be a very costly defence. Especialy if the good guys have a hundred or more very good people.
Sounds like a modern Thermopolye set up only with better odds for the good guys.
If the duster drivers are willing to go up against the RPGs, any dust will do a lot to scare the whey out of the bad guys. Malthion being relatively harmless will make em think they have been poisened.
Establishment of communications with the regular forces coming to help will be nearly manditory to avoid taking heat from their advance units. Friendly fire isn't.
Molon Freekin Labe bad guys.