The sheriff takes issue with your histrionic description of the encounter:
‘Why didn’t he just sit somewhere else?’ Sheriff rips apart ‘Stand Your Ground’ defence of ex-cop who shot dead father for texting in movie theater
http://www.freerepublic.com/focus/f-chat/3112725/posts
The Sheriff is wrong.
"Stand Your Ground" provides immunity from prosecution for people who may have had an opportunity to retreat but choose not to do so.
The burden is on the prosecution to prove that self-defense was not justification for the shooting. There is no burden for the defendant to prove that he couldn't retreat.
Prior to passage of the "stand your ground" law there was probably a legal duty to retreat, if it could be done safely, rather than use deadly force. That legal duty no longer exists. Whether the Sheriff likes it or not, a person who is attacked is not obligated to retreat (subject to some exceptions).
A part of the "stand your ground" law also details how an accused may avoid prosecution. I'm not sure of all the details of who has the burden of proof and what level of proof is required.