I don't think his "candy addiction" thing in Company Picnic exists in the other episodes. He ate a candy bar in Smunday w/o going crazy, and was around cake and ice cream in Hal's birthday without going crazy, um, what else? He had Ice cream in Long Drive, Mrs. Tri county, Book Club, Evacuation, Jessica stays over, and probably some others...he found an M&M in polly in the middle and didn't go crazy over it...he didn't go crazy when Lois said she'd make him cookies in Buseys Run Away...He was at a table with cake in Kitty's back and Hal sleepwalks...oh, he also had ice cream at the ranch in Malcolm's job...he was calmly eating gummy eels in Sleepover...
To contradict, he did try to sneak stuff from a dessert cart in dinner out and went crazy over some chocolate frosting in sleepover...and went crazy after drinking sodas in "The bots and the bees"
Is it sad I know practically episode-for-episode what Dewey has eaten?