Best guess is that Mark simply wants to go to the military from what he's saying... But why would a journalist get a scoop like this and keep the lid on it unless they go missing?

Val's paranoia does seem much more healthy though. She's open to the idea of going to the military but also aware that once that step is taken there's no going back and no protections unless they have a backup to cover them in case of misdeeds.

Gharr certainly wanted to go straight to the military or leadership and as he gets further across human history and present he might start to question Dan's argument against it.

Probably the best thing Mark and Val could do is actually start brining it up with Gharr and simply note that Dan's distrust could be unfounded and ask if he really does want to contact authorities or at least come up with a planned way of doing so.

Erm, Mark? What exactly do you plan to tell that journalist that'll a) get him interested to stay in contact with you, covertly, no less, so as not to get caught with you, b) will keep him interested to the point of publishing something after realizing that the entire government's going to come for him afterwards, but c) does not prompt him to grab y'all in a death grip so as to see every second the scoop of the millenium unfolds with his own eyes?

I don't think threatening a dead man's switch is going to fly with the military...

Threatening a DMS to the military just makes them think that the consequence of shooting you is inevitable, so they'll just shoot you anyways.