Hiya, the system of Fort is a bit strange but once you fully understand it, forting will be your hobby!
So you're right about 2nd place receiving 8000 gralats, but you might have misunderstood how the actual system works. You don't actually get the 8000 gralats each, it is divided by how many members there are in your gang. So if you all got 750 gralats, it would've added up to the total cash prize.
For the guy in your gang issue: The only way he can get out of your gang is if an admin disconnects him. However, he must've relogged at one point to sleep or eat... Buuuuuuuut, if you're 100% sure he's in your gang, show me a picture of his profile, and send it here, and I'll see what I can do