In regards to coyotes 'jumping the string', yes, even moreso than deer. Coyotes are far more reactive than deer. In general, however, coyotes will "duck the string" rather than jumping.

It'd be irresponsible for someone to answer about the drop characteristics of your particular crossbow without knowing more about it. Easiest answer is to get into the stand and practice a few shots to see where it impacts relative to your site.

The complication between shooting downhill or out of a stand is usually due to the difference in viewed distance vs horizontal distance, and then the difference in drop compensation factored into the site. The TOF to cover 30yrds changes a bit, but not hugely, and frankly, I wouldn't expect a huge difference between the two considering most modern crossbows (fast enough that they don't change point of aim much from 15-30yrds).

One warning: If you're shooting coyotes with a bow or crossbow, be sure you have a lot of bolts/arrows handy, and plan on losing all of them. That's part of the fun of it.