Yes, you can be charged with a battery. It does not have to be a violent touch, just one that is unconsented to by the victim. If it is your first battery charge, it will be a first degree misdemeanor. Contact an attorney immediately to begin preparing your defense.
What a witness says is not under oath, but if it is included an affidavit then the author swearing the facts in the affidavit, meaning that the officer is swearing that the witness made the statement, not that the statement is true. Sometimes non law enforcement witnesses do write sworn statements, and the witness would swear to the truth of the written statement. Contact attorney to discuss the credibility of the witness statements in your case.
More information is needed, but this case possibly falls into Florida's 10-20-life gun law. If so, he faces a minimum of 10 years. With these charges he is facing a maximum of life in prison, but given his age, such a sentence could be considered unconstitutional.
You are not a convicted felon given the information you provided. However, read the question carefully, as it may also include withholds of adjudication. You should contact an attorney to see if you are eligible to have your record sealed. Contact our firm in Clearwater for a free consultation.
I agree, it only takes one witness, and their testimony alone can be enough to convict. Talk to an attorney about the strength and weakness of the case, as the less evidence there is, the more difficult it will be for the State/Feds to prove the case beyond a reasonable doubt.