Try maneuvering the airplane in simulator at high altitudes and judge your comfort level yourself. See the airplane reaction
You seem to be traumatised by your sim experience. Every batch during type rating is given handling at FL350 and shown that even at bank angles of over 30 degrees there is substantial margin between MMO and Valpha prot/ Vls. I am sure it was a sim problem. The accidents that happened were because the pilots yanked the stick back in alternate law. Had they done nothing it would have been safe. If you compare CFIT accidents you may change your opinion.