as far as nose down issue when jumping, take a look and see what your ride height is and watch how the vehicle leaves the face of the jump, make sure its not slapping its rear end on the jump.

If what I am seeing of pics of the car are right, it has its weight oriented forward like the Tekno SCT410 in a way, which also was notorious for a nose down jumping issue that to get mostly corrected involved some spring, piston, and oil combo changes I believe.