As for why he didn't mind revealing and even selling those potions later on? naturally, it was because they were going to spread it around anyway.
The first dungeon has already appeared and been cleared. Since there was a first there must be a second and a third.
This means that the health and stamina potions in his position were extremely rare right now. But not long after the value will drop since other people will be able to acquire them in other dungeons.
So basically, he was going to lose out if he kept them for too long. Of course, his plan to sell the potions will take a certain amount of preparation and planning.
After all, these kinds of things can go wrong very quickly.
Esdras, Celine, and David made their journey back to the fortress, of course, they were going the long way around.
Even though it might be longer and harder through the forest it was the safest option.