I was out driving when mine tore... and it was immediately manual brakes ... a lot more pressure to stop the car... no mistakeing it... and it would not shut off by the key also...
The amount of oil was significant visually but not gushing... I drove the car , to get home , about 20 miles.... if that is any help... on my car the oil was inside the aircleaner because of the position of the tube from the pump.... but I don't think all are that way..
I think your diaphram is ok from what you have described....