No, he was out running a personal errand.
identified a situation that was abnormal enough to contact the 911 emergency number and request the police.
No, he called the Sanford Police non-emergency number. I think that is an important distinction for several reasons.
He then attempted to maintain eye contact with the suspect
He lost sight of Martin while still on the phone with police. It is fair to conclude that he attempted to spot him again after hanging up - not "maintain" but "regain" eye contact.
and when he lost sight of them, returned towards his vehicle when he was attacked and viciously beaten by a punk kid who tried to take his firearm from him.
That, reportedly, is Zimmerman's version of what happened. To date we have seen no witness statements as to how the fight actually started. Absent such witness statements, of course, there is no evidence to either support or contradict this version.