Your husband appears to be charged with Aggravated Assault with a deadly weapon, which is a third degree felony and punishable by up to 5 years in prison. Since he allegedly used a firearm in the commission of this felony, he could be looking at a 3 year mandatory minimum sentence on that charge, pursuant to Florida Statute 775.087. He is also charged with a misdemeanor battery, which is a first degree misdemeanor, punishable by up to 1 year in jail.
So to answer your question, his worst case scenario is a maximum of 6 years in prison with a mininum of 3 years. The judge could also give him a term of probation.
The best case scenario is that the prosecutor has insufficient evidence to prove the charge and dismisses it.
In addition to your concerns for your husband, you must also keep your own interests in mind. If you are served with a subpoena to appear in court and you fail to appear, you may find yourself in contempt of court. If you do appear to testify and lie under oath about what happened, you could possibly face a perjury charge. If you previously told the police that your husband did commit this crime, and subsequently tell them or the prosecutor that it didn't happen, they may try to charge you with Giving a False Report to Law Enforcement for your initial report.
Your husband needs to consult with an experienced criminal defense lawyer to discuss the specifics of his case. You may want to seek out your own lawyer if anything in the previous paragraph applies to your situation.
I concur, with one exception, and some additional thoughts.
First, the exception: Is this a 10-20-Life case? There are certain circumstances where a prosecutor may decide to file it as such, thus increasing your husband's liability. How the police file the complaint is not necessarily how the Assistant State Attorney will file the charge. Here, the "weapon" was a firearm.
Second, is your husband in Division I, II or III? Judge Brown, Judge Stone and Judge Flowers are all different judges.
Third, who is the prosecutor? This is a critical question. The prosecutors are different, too. Knowing the judges and the prosecutors is critical - it affects every aspect of the case.
Finally, the worst case scenario: Your husband tries to handle this case on the cheap and hires a payment plan lawyer. Payment Plan criminal defense lawyers have cases falling out of their ears. Their crushing case load is as bad as the case load of our overburdened Public Defender system.