55 IBUs doesn't seem like too much; millenium's bittering power is greatly overstated (in my experiences with it), and the same is generally believed about any hops added in the last 15 minutes. 4lbs of wheat and oats should soften the dryness and bitterness as well. 5oz of coriander sure seems like a lot. Belma, centennial, columbus, coriander and 3944; that's a lot of flavors. I hope they work well together.
Say no to intolerance: love gluten and lactose.