I don't know if you can "keep from being intimidated". I mean, you're either intimidated or you're not, right?
So am I to be considered a psychopath, because I have no adrenaline rush and actually get calmer as things get chaotic? The last Yard riot I was involved in, many said they thought we were conducting a drill because my voice was so calm. When incidences occur I usually take control, because I seem to be able to think more clear and slow everybody down.
re 1.: You can experience feelings that tell you that are experiencing being intimidated. You can also override the feelings (not struggle against them, just accept them and not be ruled by them) and show no outward reflection of the feeling you have and act based on not allowing them to rule you.
re 2. Not psychopathic. Besides training to deal with stuff, not all people are wired the same. Some don't have typical adrenaline rush in situations the majority would, and some have parasympathetic response instead of sympathetic (slow pulse, dropped BP, etc).