I would up the roasted barley quite a bit and reduce the chocolate. For my usual dry stout (see my recipe dropdown) I use 500G in a 25L batch. That's a little over a pound for 6.5G. You won't get a lot of roasted flavour with 3oz. The chocolate will give you a different flavour. On the other hand it should go really well with the vanilla. So I guess that's a roundabout way of saying, yes: it looks good.
Go easy with the vanilla though, that stuff is powerful and it's really easy to overdo it.