Given that Impressive sired 2250 foals in his lifetime, I think the fact that you have a nutso horse who also happens to have Impressive are completely unrelated. If you own a QH or Paint, there is also a strong likelihood that he/she could have Impressive in their background.
I have a filly born this year by a stallion who goes back 5 generations to Impressive. My reason for choosing him was that he was so extremely calm and docile. My young nephews came with me to look at him and they were brushing and grooming and making noise and he barely batted an eyelash.
She is much the same. She stands stock still when I bathe her, has no issue with being sprayed with fly wipe, spot remover, show sheen, picks up her feet, has had her feet trimmed with no issue, doesn't mind being touched anywhere and tries really hard to do what I ask if she thinks it will get her a "good girl" and a scratch.