Thank you for your patience. First of all, you need to understand that Florida is an at-will employment state. At-will employment means that without a contract, you have no contractual or other right to employment with the company. The company is entitled to fire you for any reason: a good reason, a poor reason, or no reason at all--as long as the company does not fire you for an illegal reason (race, gender, age, religion, etc...). But it extends beyond firing, to hiring, promotions, demotions, wage cuts and raises, disciplinary actions, and even scheduling. Unless you can show that this was done in violation of a contract, union agreement, or a clear violation of an unambiguous and binding clause against the employer, or that it was done because of some minority status (age, race, gender, religion, disability) that you have, then they do have this discretion.
Florida law does not require employers to provide employees with severance pay. If an employer chooses to provide severance benefits, it must comply with the terms of its established policy or employment contract. Now it can establish a policy by "practice" rather than written policy, but to establish any sort of discrimination, you would need to show that one class of individuals was disproportionately benefits (for instance, only males got severance packages and females didn't) to have a claim of discrimination in that matter. As for the "leverage" to negotiate a severance package, it doesn't sound like you have much, if any. Again, Florida is an "at will" employment state and employers have discretion in this regard. Severance packages are generally offered in exchange for the signing of a waiver of any claims that you would have against the company, if any. If you had evidence that you were targeted for race, age, gender, religion, etc... then you could use that as leverage to get a bigger severance (because you could make a claim otherwise).
As the law doesn't require that they provide severance, any severance provided can be done in conformance with their policies and conditions, so if they have not stated that it's "unconditional" or otherwise "earned" by you, they could take it away, especially if you refuse to perform job duties that they describe. Basically, they can terminate you prior to laying you off because you refuse to do what they tell you to do. I'm not saying that they will, but they legally can. It's unfortunate, but it's what is legally allowed.
I know this is probably not what you wanted to hear, but it is the law. I hope that clears things up anyway. If you have any other questions, please let me know. If not, and you have not yet, please rate my answer AND press the "submit" button, if applicable. Please note that I don't get any credit for the time and effort that I spent on this answer unless and until you rate it positively (3 or more stars). Look for the stars on your screen (★★★★★). Thank you, ***** ***** luck to you!