The things you list would not, as a general principle of law, have any effect on the legal question whether you actually owe the dues. Affirmative defenses in this context means "reasons you don't owe the debt." Consult a Florida lawyer who handles collections on behalf of debtors to explore the question whether the things you list would have any effect in an action by the HOA to collect on a judgment. (I.e., "reasons you should not be required to pay all of the debt all at once.")
Not legal advice as I don't practice law in Florida. It's just my two cents on the facts you describe in light of general principles of law. If you need legal advice, please consult a lawyer who holds Florida licensure. That's not me as I practice in Vermont ONLY.
I am not licensed in Florida. I am licensed in KY and IL so you may want to consult a Florida attorney. That said, keep in mind when you are sued on a debt, it is the burden of the one suing you to prove that you owe the debt. The finder of fact is either a judge (if it is a bench trial) or a jury (if it is a jury trial). The finder of fact is supposed to determine whether you owe the money. The factors you asked about all deal with your ability to pay the money, not whether you owe it.
A lot of times you can figure out what the law is by logical reasoning. For example, if the law were as your question suggests--that someone could escape responsibility for their contractual obligations by arguing that life is tough for one reason or another, then we as a society are fostering a culture of whining excuse makers that are rewarded by coming up with good sob stories. If that worked -- in other words-- if that were good enough to win when you are sued, then everyone would do that. No one could ever win a suit for breach of a mortgage, or a lease, or failure to pay a bank loan. Then what would happen? What bank would ever loan money to anyone? No bank would loan for homes or cars or anything. The risk would be too great. Now, if that were the state of things all brought on by allowing defenses as you are contemplating, who could buy a house or a car? Answer: only the rich could buy one -- those who could buy it outright for cash without having to borrow. Do you think politicians would pass laws that would effectively make it so only about 2-3 % of the population could buy a house and only a few more could buy a new car? This would devastate the auto manufacturing and housing industries. There is no way they would allow that to happen. Conclusion: they did not allow that to happen. No such law has been enacted to let you win your suit by saying my income dropped or I got cancer. The closest we have to that is our bankruptcy laws. If you find yourself having lost the suit and being unable to pay the judgment due to the hardships you referenced, then you may be a good candidate to seek relief in the bankruptcy court. For that, you need a good bankruptcy lawyer. My answer may have sounded sarcastic. It was not meant to be. I was simply offering you a different way to think things through that might be useful generally in life.
To aswer your question - No these reasons are not legal defenses. No you cannot expect "mercy" from the court. HOA liens are governed by Florida Statute and hiring an attorney to defend you is critical. HOA liens, once properly filed and a judgment obtained, can force the sale of your property to satisfy the lien. You would have a right to redemption (i.e. paying the debt in full to keep the property), but if you had sufficient funds, you would not be in this position. You would be able to postpone collection of any judgment by seeking bankruptcy protection, assuming you are eligible, but that may only postpone and not prevent a sale. Seek legal representation immediately.