If they're concerned I'll lose some or all of the account value at the same time as I default on the loan, they could roll the contribution money into an identical account at their institution where the only investment option is cash (or whatever they consider safe enough). 

Then looking closer, I see that there are two identical neighboring triplex for sale.

That means they will take the will to court and verify that it is legit.

Does the story make sense, and have you checked the local district court to verify if there's anything more?     

I was excited about the deal, so about 10 days into DD I decided to make a last ditch effort to save the deal and verify the sellers claims that Pizza Hut wanted to renew their lease.

(obviously my mistake) So 2nd time almost identical issue, on the 5th tenant came by after hrs with no phone call or acknowledgement that they had left payment except this time we saw the car leaving so i called (of course no answer) but left a very stern and detailed message about how this was not acceptable and no longer will be tolerated. 

If you are sourcing the property from a broker, ask them to provide you with the 12 month trailing financial for that property so that you can verify and accurately estimate the expenses.

You should verify that with an accountant.

We have pulled their credit reports and the credit reports say that SSN could not be verified for both the husband and wife.   

This terms look identical to some portfolio lenders I've come across.