Is Dimension Door a save-or-die spell on purpose now? is level 4 low enough for that kind of stuff?
We used it this way in my old campaign, but YMMV. Beside that, it would be nicer with a range longer than 10', to be used to fetch things as well 
Re:halflings: i'd make the thrown weapons attack roll rise as fighters. Move silently would also fit the kind of "i'm just good at sneaking into places" character. Personally i used halfling progression (with thief ST and no level limit) for pygmies and human rangers.