A couple of thoughts-
If icing was present as seems to be indicated to the extent it would affect the pitots then what would extensive airframe icing do to the AUW and was there any indication wing anti ice was being used?
Secondly I find it hard to reconcile being able to achieve a 7000fpm ROC in two and a half thousand feet from F350? Even if it was possible the ballistics and KE of a 205 ton aircraft going up at that rate would see it going quite a bit higher IMHO. In a light aircraft at lower levels it is extremely rare to see more than 6000fpm with a light aircraft never mind the pitch rate to achieve that ?
So maybe external forces were more of a factor.
Not sure Simulators would be able to accurately reproduce this situation with no empirical data.