I just wanted to put in my 2 cents worth with regard to the accelerant. IMO, the lab results must be back by now and known to the LE agencies that are investigating this case. I also believe that any test results will not be divulged until such time that a trial (& we hope) takes place. This may seem trivial but I feel that LE would not want the killer(s) to be alerted to the accelerant information that they have in their possession (MOO). I'm sure that when they do have a suspect(s) search warrants will be obtained for his/her/their houses, places of work, vehicles etc. They would search for any accelerant that may be stored at the latter. Yes, this is a long shot and any containers may have been discarded a long time ago. But then again, maybe not. Evidence of this nature would be particularly valuable should it be something more unusual (unlike gasoline). In many cases, LE doesn't divulge evidence from a crime scene since it would be known only to the perp(s) and LE.
As an aside, I have many American relatives, two of whom live in Tennessee. These are cousins who are very dear and close to me; one born in Kentucky and his wife in Mississippi. She still has several relatives in MS. I'm going to call them to see what they think. They know I follow crime stories! Lol! In fact, during one of our Tennessee visits, Mary Winkler killed her preacher husband and took off for the Gulf coast. When she was released on parole/custody (I just forget) these same cousins saw her working in a dry cleaner shop in a town not far from them! Sorry for the OT but just wanted to throw it in.