He broke the rental agreement on more than one occasion and abused our friendship (to an extent) to move out early. 

Was there verbal or physical abuse that needs to be reported to authorities?

It sounds like a great idea on paper to check on the condition of your property and see if the tenant is abusing the place.

The FRAUDS AND SCAMMERS have abused it so badly in FL that FL addressed using contracts to circumvent licensing in FL Statute 475.43. 

Someone on BP said a deal is like a bus, there is always another one coming around the corner.

. §§ 90.396, 90.40324 hoursViolence or threats of violence by tenant or a guest; intentionally causing substantial property damage; giving false information on an application within the past year regarding a criminal conviction (landlord must terminate within 30 days of discovering the falsity); committing any act “outrageous in the extreme” (see statute); intentionally or recklessly injuring someone (or placing them in fear of imminent danger) because of the tenant’s perception of the person’s race, color, religion, national origin, or sexual orientation; second failure to remove a pet that has caused substantial damage

Parents were (righteously) pissed and had him charged with sexual assault.

I'm wondering if I should mail them a certified letter stating that I am blocking their access to the tenant website due to abusing the hold days and tell them they will need to send a certified check to my PO box on or before the 1st of the month.

Alien abduction of the window screen I have not yet heard or seen, though...It is just one of the many wonders of landlording (along with common sliding closet door abuse)...I have no firm answers or solutions.

If you tenants have cash flow problems, there are several things you can do:1) Spend a lot of time working with them, catering to their specific situation and cutting a lot of slack (very likely to be abused by tenants in general--there are exceptions)2) Be a complete hard-nose and send eviction notices the second they're late3) Find a way to help manage the cash flow problem, aka make debt collection someone else's responsibility.