First, the repair problem should be brought to the landlord's attention in writing by certified mail. You may end up in court and certified mail is the best proof of delivery. Second,as long as you are living in the house your landlord is entitled to rent, with some limited exceptions that don't seem to apply here. Remember that you can always negotiate. Discuss the matter wit the landlord after sending the written notice and see if you can lower the monthly rent even more.
The mere fact that you ask this question makes it clear that you need an attorney to prepare the answer for you. If you must file the answer yourself, be sure to respond to all allegations in the lawsuit. Do not just file an explanatory letter. For example, in credit card cases the defendant often writes a letter to the court explaining the hardship they have gone through. That does not help your case. The judges have seen those letters many times. You must address the specific...
The statute requires that the outstanding rent be paid to the court registry. The attorney can hold the money in the registry and file a notice with the court stating that the attorney has the money in trust, but the court is not obligated to treat it as if the money was deposited into the court registry.
Consult an attorney as soon as possible. If the attorney confirms that title is still in your name, then you don't need the mortgage company to give you the keys. You can get a locksmith to change the locks and you take possession of your home. If someone is living there you may have to file an unlawful detainer action to get them out.
Florida makes the owner of a car liable for injuries resulting from its use. So in addition to purchasing adequate insurance, the car should probably be titled in the daughter's name and keep your name off to limit liability.
Whether you can raise the rent or make a new lease depends on the terms of your current lease. You may have to wait until the lease ends and then change the rent terms if they want to renew. Talk to a landlord-tenant attorney about drafting a new lease so that you can rent the units separately and address the separate units.
When the tenant is resisting your efforts in that manner i don't recommend showing the property. You can serve a three day notice and then file an eviction action or wait for the lease to end then file your eviction but you probably need to evict the tenant. If they have not paid in two months they may be planning on staying as long as they can.
Consider placing a sign in the rear window that states "Tag stolen" and list your current tag number, also state that a replacement has been ordered. That should put them on notice that your car is not abandoned and that the car is registered.