Algae pool, in the context of a list that contains "balanced nutri*nt? foods", is probably a food based in Spirulina. A green algae used in aquaculture. This seems to me like a check list [1] to assure that he didn't forgot anything after leaving a zone.

Is relevant because the man has been most probably poisoned. It was not a fast poison and it was painful but not too alarming. Not a bee, a wasp or a Bothrops. A plant or fungus, yes, could fit.

Is not suicide and terminal illness in my opinion. Nobody dies by starvation in presence of food.

But there is a third category that I was missing. Your own food. A too old Spirulina package can be contaminated and lead to slow poisoning. Emaciated in the context of plenty of food around and plenty of money means that he was deliberately refusing to eat while resting in the tent, this is a common effect of food poisoning.

[1] Speculating "Roach motel" can be an humorous surname for their tent. Nanites could be some kind of "armour", clothes or boots maybe.