Can't help you with the insulation, but we've been using the Damp Rid
Hi-Capacity Moisture Absorber
in our boat and it's really helped keep the moisture down.
We keep one in the head, and one in the forward berth. We get them from Home Depot.
I've learned for you that if the bucket is dented (ie "possibly cracked"), don't buy it. It will give you a new appreciation for how much moisture the bucket absorbs, but not in a good way.