What is clear and your statement emphasizes is that the prosecutors who initiated this brouhaha are aiming at having another charge against Zimmerman should the 2nd degree conviction fail. Clever, just like the Feds nailed Al Capone on tax evasion.
That's doubtful. Perjury is actually one of the most difficult (if not the most difficult) crimes for a prosecutor to prove. It is very difficult to prove, beyond a reasonable doubt, that someone knew they were lying, and it is very easy for defendants to argue that the questions were vague/misunderstood/etc (think Bill Clinton's "depends on the meaning of 'is'" nonsense). It would be extremely unlikely that a prosecutor would use a perjury charge-particularly one arising out of a bond hearing like this-as a "fallback" charge in case they fail to get a conviction on other charges.