That's not bad at all given all the modifications! You added some weight for sure in some places but definitely lost it in some others. But not bad at all considering you haven't gone too far out of your way to make it lighter.
I would suspect that scale has to be certified and is checked/inspected on a regular interval. It might not be accurate to a couple pounds and it won't give you corner weights, but I would bet the overall weight of the car is pretty darn close to that.
