CubeSmart, LP False Eviction, Property Damage, Negligence

My daughter rented a storage unit from CubeSmart (CS), first month free.  CS gave my daughter a combination lock to put on the unit.  While still in the free month period, I got a call from CubeSmart, asking me if we were still using the unit "because it looks like you only have a mattress in there."  I asked how this was known, and CS informed me that it had taken it upon itself to go into the unit and look, and that it's their policy to do so when you use the lock they give you. 

I informed CS that, yes, we're still using the unit and that more items will be placed in it.  2 days later my wife went to change the lock and discovered that the mattress was no longer in the unit.  She contacted on-site staff, who stated that, despite being informed 2 days prior that we're still using the unit, he thought the unit was abandoned and that the [$2,300] mattress had been moved to another unit where they keep abandoned property. 

When they took my wife to that unit, she discovered that

(1) The mattress had been thrown on top of other peoples' mattresses, raising a concern over bed bugs and other contamination, and

(2) CS apparently dragged the mattress a considerable distance across the parking lot to another part of the facility, leaving black marks from the asphalt on the mattress and tearing its fibers.

For 3 weeks now we've been dealing with CS's Paul Fleming, who is tasked with resolving the issue to our satisfaction, but who is essentially worthless in this task.  Despite our repeated warnings that our patience are wearing thin and that we're considering legal action, CS stalled the process well beyond a reasonable amount of time before offering to have the mattress cleaned and treated for bed bugs, but only if we sign a form

(1) waiving our right to hold CS liable for the damage they caused and for ANY FUTURE DAMAGE they may cause, and

(2) waiving our right to ever tell anyone what they did to us. 

We informed Paul that we would sign the form if CS were to limit it in scope to the incident at hand (not to future incidents) and remove the clauses that limit our right to speak about the incident.  We've not heard back from Paul or anyone else at CS since, so now we have to take other actions.