There is not such thing as Tomexide. It isn't any kind of pharmaceutical or even a brand name, there's nothing remotely similar so it can't even be a case of an actress mispronouncing an unfamiliar word.
The closest word that does exist is Tomecide, which is the burning of books.
No sniper would take a shot, on a moving target, with that much wind. Along with the elevation and steep angle there would be no predicting the bullets path with the required degree of accuracy.
When the assassin pulls the bolt back on her rifle to chamber a round, the bolt doesn't open.