Not sure about height of tire off the ground, but she drove 90" up the ramp. If my math is correct with the WB of an XJ at 101" ; 90 / 101 x 1000 = 891
Your math is right,90" up the ramp would put the tire 45" off the ground.
That's a lot of flex,there's XJs out there with linked rears that don't score that high.
So if it was really a 30 degree ramp that's pretty impressive.