Black in magick isn't always used in a negative sense. If you found rust water spots, then I would be suspicious of foul play.
Since you are obviously knowledgeable enough to use sage and salt on your home, I presume you have some knowledge in omens and signs? Instead of blaming your neighbor, I would instead consider that this was a sign of the impending illness that struck your family. Blackbirds, especially crows and ravens are considered messengers from the spirit world. It is not at all inappropriate to cleanse a home by magick means during illness to speed recovery. Our ancestors did so too because they believed malicious spirits to be the cause.
The best way to handle this is to calm down, recover from the illness (this is the flu season after all), and continue with the sage and salt. With your panic alone, you could create a curse on yourself and your family. You need to find confidence in something to protect you so that you feel comforted and safe so that this doesn't happen again.