Wow dude, chill. Fuck the mall, first off. The only store that has any sort of extensive LRG collection is Zumiez. Zumiez is the spawn of fucking Satan. The only reason I ever go in there is to see what LRG stuff NOT to buy. Besides, they usually only stock up to 2XL in the store. To find 3-6XL you have to hit up Eastbay, Dr Jays, KL or some other online store.
As for sizes, Zip hoodies run bigger than Pullovers. Id say a 4XL zip or a 5-6XL pullover if you are looking for Harlaut style sag.