Both work, experimental flight model will have some minor performance differences, but advantages in other handling areas. It is up to you.
That sounds like a bug - issue logged
Experimental aircraft with no published G-limits. We don't simulate the wings snapping with overloading as in reality the control authority and possible control force would be the limiting factor.
CG is most likely fine - the aircraft has a pretty darn high lift wing and when you get it to fast speeds, it is generating a bunch of lift -- too much actually. Nose down is to compensate for that. Most planes with a more narrow operating envelope wouldn't have this issue, but this plane is a bit unique.