First off, not really sure how you are getting an R-30 rating in that wall. 1" of closed cell is worth somewhere be 6.0 and 6.5 R-rating. Best I can calculate you may get to R-19 in the walls. 2 1/2" of blown cellulose will net you about 10 R value. This gives you 16 - 16.5 R value between the studs. This is assuming you have 2x4 framing. Gets a little better if its 2x6 framed exterior walls.

For your zone you would need about 12" of blown in cellulose or half that amount of closed cell.

The Tyvek wrap on the exterior walls helps to keep the humid air away from the home. Your attic on the other hand is vented and has a direct link to outside air. This is why the attic is more important to have a barrier.