I really like this. It would likely benefit more from a bonus to STR or CHA.
Under Stalking Child Thief, I'd recommend you put "equal to half his total HD" to be 100% clear.
Change applied.
Yeah Str is definitely good for them, and while they only have two effects that scales off Cha, which one ist easily usable in combat, the other is a solid demoralize effect in combat, so it is not a bad choice depending on what classes you branch into.
It gets Dex to stats though so it can stealth a little better on top of its skill bonus. I can probably change this to provide a bonus to both str and dex though (+1 Str 1st, +1 Dex 2nd, +1 Str and Dex 3rd).
Actually this can probably use a little more scaling off cha. I nerfed Creature in the Dark so the teleport can only be used once per minute, but also let the krumpus reset it a number of times equal to his charisma mod each day in case he needs to make multiple dashes in quick succession with it. Also gave it a clause that it resets it whenever he grapples someone into his bag, as a reward for being successful with its base class feature.
Also gave the teleport some more versatility at higher levels.