In regards to 5, I was very paranoid about this too, but its very hard to do. They normally just move out of the way.
I've been told, if you do suck them up, they will just stick themselves to the inside of the vacuum, and not actually go very far + its not powerful enough to pull them up, so they'd just fall back down like the gravel does.
You can just feed them vegies, like courgette and peas, you don't need to buy a commercial food. Make sure there is some driftwood in the tank for them to chew though.
There are heaps for sale on trademe, they're probably healthier than shop ones cos they won't have the stress of being moved about as much (And their 'parents' will have taken better care of them than certain pet stores.....)