I could suggest only a few things.
I think you should pay a visit to your property and take photographs of everything and the condition of everything closely. If it breaks between now and 28 days, a judge would far more inclined to believe the damage was intentional if its within the last 28 days.
I think you should text or email the tenant and ask them when they paid the deposit and in what form, and inform them that any threats made of theft will be reported to your legal representation. Hopefully you can get a reply from them stating some rubbish about the threat so you have a written record.
Also failure to prove they paid a deposit would work in your favour too.
If you need to, near the end say you will meet them the day after the end of the agreement and 'deal with thier request'. You have two ways of doing this, meeting them in the apartment for an 'inspection' of the property so you can see if anything is need of repair.
Try to make it sound like you are assessing whether you could deduct from thier deposit without being too obvious as you dont want to look like you might have it on written proof. As they are due to move out, bring some help with you(cleaners
) so you feel safe, They are obliged to leave. Then explain to them that you remember no deposit, and that they have no proof of it, that you have a contract showing no deposit SIGNED by them, and that they cannot show you anything which suggests they paid a deposit.
Basically just make them hang on till the very end waiting on it, when you are there, they are not going to touch your property, and you should definitely bring some male support along incase they try to forcefully remove your property.
They have every right to bring you to court or judgment but that would be a win for you so its just trying to avoid that last akward day imo.
In all cases where i've rented, the landlord always inspects on the last day when im due to move out, so its reasonable enough.