first off, sorry for not being around to get your messages tofay. but yea, i would definitely see into doing something to tend that wound. it's very hard to tell for sure, but it looks as though it sustained that pretty recently, possibly could have happened from mishandling in shipment. as for the mites, you can try the oil trick, but i would be careful near the wound if any mites are there. i would also be careful using any special reptile mite spray if it will possibly get in the wound. a lot of geckos have delicate skin that breaks easily, so it's also possible the injury poses no immediate threat, but its best to cover all bases. as for hydrating it, the open mouth thing could have been it's threat display seeing as its very likely to be a bit stressed right now, going into the shower might have been enough for it to feel threatened. so either go back to the shower tomorrow for a short while, or go back and try the pedialyte method. as i said before, this method takes a lot of time, seeing as for the most part you just put a drop on the snout and wait for it to be licked up. if you stay close enough and wait for the tongue to come out, you can manage to get a few extra drops in during that brief moment. just keep at it and things will hopefully get better.
good luck
