Although a matter of taste, "Blood" is one of my personal favorite X-Files standalone episodes of the entire series. Yes, it was LSDM. Now here is where it gets a bit tricky: Mulder says to Scully that he believes the LSDM is causing the heightened fear and adrenaline, but that the messages on the various displays are relayed "purposely" by someone conducting a controlled experiment, in order to see how they'd react. I have to disagree with Mulder's theory there. The most rational explanation IMO is that the substance simply makes them see the messages, and there's no one really sending them. It's one thing to send messages through a cellphone or computer screen, but a totally different thing to do it through a microwave, car dashboard, elevator display, etc.
I also thought that the ending was interesting: "ALL DONE", "BYE BYE". This tells us that the chemical affected Mulder as well, although not in the same way as the others. Clearly the substance does not affect everyone. Having a phobia certainly plays a role, but there might also be something else the individual needs to have, in order for the substance to trigger the hallucinations and murderous impulses in him/her. So, since Mulder "fears" that this is a conspiracy where someone is actually relaying messages through these devices... maybe he sees that which he fears... a message from "them", those who were conducting the experiment (as he thinks), saying that the experiment is finished. It could be interpreted that his hallucination tells him "they", the conspirators, just got away with whatever it is they were trying to accomplish.
Regarding the blood tests / folks ringing the door bell, that's how Mulder and Scully were able to locate Edward. He was on that list of people scheduled for a possible test. You touched on something very interesting which is how/why the display told Edward that they're waiting for him. My explanation for this is that he "read" part of what was in his subconscious mind. He was, in the bus, probably afraid of getting caught. Although not actively thinking about it, but perhaps deep inside he was afraid that they were waiting for him, hence the message on the display.
To be clear, I'm not saying there's no possibility that this was an experiment to see how humans would react to the LSDM. That could very well be true. I'm just disagreeing with the "messages relayed on purpose" part, in regards to the electronic devices. Either way, one of my favorite episodes for plenty of reasons. You also recognized "The Lone Gunmen" (Langly, Frohike and Byers) right away, who were introduced in season one episode "E.B.E". It appears that you tremendously enjoyed the episode, and I'm glad.