A lot of people are basing things off the eyes of the law, but usually when you're physically attacked the last thing you think is, hmm, I wonder the procedure for this, which would look best in a court of law, ohh.. hold on, do I hit him here or here?
Sometimes things happen so fast the first thing you want to do is make sure #1 is okay, you, then how you can stop the pain by disabling the other person in the easiest/quickest/only way you can.
So effin easy to sit at a keyboard and say "should have done this and that".
However, as a security guard, when you got yourself free some restraint should have been showed and the possible outcome was that he wouldn't come back, you would have reported him and that's it.
Good idea to get that blind spot sorted too.