I would reconsider the mothballs. Bears are curious animals. Mothballs smell very strongly, and not like anything a bear has ever smelled before, which might actually attract the bear from a greater distance, just to investigate. I would concentrate on minimizing smell, not masking it with stronger smells.

BTW, I have cached for 3 weeks using a plastic five gallon paint bucket, w/ lid, on more than one occasion. No bears have disturbed one, yet. I cached in the near vicinity of roads each time, but always out of sight of humans. Usually with large rocks (15 to 20 lb.) piled over the cache. I used several layers of plastic bags, including putting the whole bucket inside a black plastic trash bag to make it less conspicuous.

Good luck.