If you wait long enough for any food/potion/spell effects to wear off and remove all equipment with stat bonuses (or make sure to take them into account), then the sum of
strength + agility + intelligence + constitution + any unassigned stat points
should be equal to
40 + 5*(Character Level) + (+5 or -5 bonus from Shrine of Good and Evil) + (+5 or +10 stat bonus from Wishing Well, if that was the wish you made) - (1 to 4 stolen by vampire in the dark cave if you saved the boy)
There was some speculation in previous topics that certain monsters might temporarily curse you, but I don't recall if that was ever verified/refuted.
You can leave items anywhere, or collect chests to keep them more organized. They will not disappear or be stolen. It is convenient to leave one teleporter stone by a bed, and collect a few chests nearby for a stash. And like Carrie said, once you have enough loot and find merchants with enough gold, a stash there is useful.
