im a multimonitor user too
i tried to use mousejail too... you cant use it because of the way you launch it.
in the end i got ultramon, and bound CTRL + ALT + L to lock the mouse to primary monitor. press it again to turn it off.
if you use ultramon, you will want to enable a margin when you use the hotkey, or the mouse briefly flicks over to the 2nd mon, then back again. i use a margin of 100px, and my mouse doesnt go over even in the most heavy shootouts