I took a while to get both 29d & 20d. The woopies one I initially thought might be greys (ie old people), being the y from levity surrounded by the 'shanks' of Grables ie gr es. Once you get it though it should be clear as the BRB actually defines the correct answer as a class of woopie!
As for 20d I kicked myself when I got it - you're on the right track with suspected misprint, can't say much more without giving it away other than maybe suggest thinking of cooler in all of it's contexts.
Now have full set of clues but hopelessly lost with the final process!