But i send him registered letters with legal threats and it seems to be working.

If not, an attorney in your area should have a skip tracer for you to serve the family with a cease and desist letter. 

Not even a lawyer .Thank you[maybe I can do better on  letter but I'm just interested in the laws on it 1st - I'm 15 days in on that 30 day limit to return or conclude deposit/costs.]Thanks

.@........ followed by ""COMmercial"" (use only letters in capital).We also wish to book directly and have payment arrange inform of a cheque.Please do forward me the following details for payment;NAMEADDRESSTOTAL FEESHope to hear from you soon,Best Regards,....................Vaccinated

In 2017, FL DOT sent seller a letter saying they might buy a portion of their land via Eminent domain with road expansion but no funding and nothing is done.

Most require you to wait for a quote and Im trying to move faster than all that.Recent Lesson Learned:  If your treating butcher block countertops or wood shelving, consider "waterlox" because it really seals in the wood while maintaining its original authentic appearance. 

The home sits on a 1 acre mostly-flat, square, and mowed block at the end of the street.

It's block by block but plenty of nice blocks exist. 

Then I wrote a simple letter with my contact info. 1:2 call back but no deal.

Have a lawyer write them a FU letter.