Yes the rounds property is the one you are looking for, it counts whole rounds, that is: once all players have moved and it is your turn again, so you cannot achieve what you are looking for one round means "untill is your turn again" while zero rounds would mean "once your turn ends (before aliens start their turn)" - that is, if zero is even a valid value at all (don't remember right now)
As for civilians walking on fire, yes it is a bug (it even has an entry on our bug tracker) currently the AI will try to not end their turn on fire (or gas, etc) unless other more pressing issues force them on it (might need balancing) but sadly that doesn't preclude them from trying to cross the fire to get to the other side... of course the same applies to your soldiers: if you don't pay attention they will happily walk into the fire when trying to get somewhere else, instead of going around... (but then, they stop walking the moment they are hurt, so won't walk themselves to death, unless you are too stubborn)