I'll still find a lawyer that can advise me whether I have protections / ability to retrieve my deposit at a minimum since the seller is able to sell the home at a higher price, and hence suffer no loss. 

She went on to tell me that I have to contact a biohazard company to clean up the fluids and smell because she wants to access the apartment to retrieve some of her possessions that she left there.

A week later their daughter returned, with a sheriff escort, to retrieve their personal stuff & the last we heard they were living in their vehicles & delivering for Insta Cart & a pizza joint.   

After a few of them not being able to be retrieved she may change her address as she will be upset by the wasted money.

Our contractor is suggesting we leave a small gap of ~3" from the wall to where our cabinets and appliances would come, but our concern is that this would lead to food/water falling through the large crack and being hard to retrieve/clean.

Have my son throw a frisbee on his yard and knock on his door to ask if we could retrieve it to start conversation?

Since I am out of state investing, its not as easy as asking the tenants if a security deposit was collected and the selling agent has been asked numerous times to retrieve this information but to no avail.Any suggestions would be appreciated.

Other then allowing the family an allotted period of time to retrieve his belongings as a courtesy, you should not be beholden to anything unless otherwise contractually obligated.

If you pay cash now, you could acquire a Deferred Mortgage to retrieve that cash. 

The locksmith arrived and within 5 minutes had the car door open and retrieved the keys.