The pythagorean theorum is actually just a right triangle and is the way to figure the distance in a mathematical form BUT due to sight paralax,the shot needs about 1 yard more taken off and that would make it about a 27-28 yard shot,according to how much sight length,peep height and arrow weight along with arrow speed.
But really we are getting way to involved for a hunting setup.Range straight out and shoot.
I am glad that you finally realized we were talking about a crossbow.Yeah,that does seem to eliminate the bending at the waist issue somewhat.But not completely.
I would say the 30' high is the real problem.