Good points there! They may have a list of suspect but no solid proof. They cannot press charges based on someone owning a dark Frontier Pro X4 near Houston for sure. About her job, I am not too worried, most jobs where you have to take critical decisions you have to sign non-disclosure agreements and they could have fired her well before she would have done something that would hurt the company. Not impossible or unlikely but I do not see how killing her would be better than just firing her. Plus if an employe is murdered, anyone else at the company that would have a concern would go to the police so I uncertain about this lead.
One thing to keep in mind on this case is the father and many of Liz familly still have the husband as friend on social media, not that it means much but to my knowledge, there is no sign of a member of the familly pointing to the husband or anyone in their friends network. I also think this person was hired but we're missing by who.
The problem with an NDA is that it may not cover illegal acts. Granted she could still be fired but she might have a civil case for being fired as a whistle blower. (Whether you're fired or not, staying where you blew the whistle is probably not a good idea.) However, you're point about someone else knowing and going to LE is a strong possibility. In any event, I believe it is a remote possibility but not high on my list.
I don't believe the husband is a strong possibility, if at all. If the husband was a predictable person, i.e., they left the house within 5-10 minutes of a certain time every day a few recon trips could have determined that aspect. IOW no inside information may have been needed with regard to when he left. Of course, if he helped her put out garage sale signs that morning he may been late leaving or if he was doing it on the way to work he may have left early.
This leaves someone who knew Elizabeth and Elizabeth may or may not have known them. Also a hired killer. Or a random killing by a stranger. There is another aspect that didn't occur to me till just now. What if this killer was not a hired killer, but was in fact killing for someone else? Someone who killed Elizabeth on behalf of someone they care deeply about - with or without the other party's knowledge - with no money involved. Yes, this person might have figured it out, but if they cannot see a connection between the truck and their related party they may not have a very strong suspicion.
Whether or not the garage sale figured into the planning is something I'm not sure about. There is a possibility that the killer had no prior knowledge of it and improvised.