Looks like you have done all the "normal" things, maybe it it time to look for the obscure. I have heard of alternators "leaking" or gently drawing (reverse drain through suspect diodes) current from the battery after shut down. Maybe, in the circumstance that you know you will not be driving the truck for a couple of weeks, disconnect the alternator BAT connection, and see what happens. A little off the wall, but if nothing else works something to try.
don
