Dive bombing in a Mustang at 90 degrees? No bloody way. 45 usually, 60 if you really push it - but 90 never.
Re the canopy. An Mustang accident near Bankstown near Sydney around 1956 I think cost the pilot his life when the canopy came off and hit his head. Same problem in a Sea Fury if the canopy was left open on take off (normal procedure) and when the pilot wound the canopy forward after take off, if his hand accidently slipped off the winding handle an aerodynamic effect would cause the canopy to slam hard forward unrestricted and maybe dong the pilot on the back of his head. Killed one pilot at Nowra and damned nearly got me on one occasion.