I live in canada and customs are really a pain to avoid. Here are my tricks :
-Go with a smaller vendor, one that does his invoices by hand (PM me if you want recommandations)
-Ask the vendor to mark down the value of the items and possibly not mark it down as tobacco but something like "fruit shisha molasses"
-Have it shipped through Regular Postal service...Just like your grandma would do if she sent you some sweet fruit molasses for christmas.
Having said that, now that you have to pay for your package, you can always get your package, pay the duties and the fill a complaint to Customs Canada. You'll have a lot of paperwork to do, but you should be able to have them re-evaluate your file. Shisha is not well understood by custom agents. You'll have to explain that the net weight of your package is mainly molasses and not tobacco.
Hope this helps you out !