Well here are the HS codes.
https://www.canadapost.ca/cpotools/apps/wtz/business/findHsCode?execution=e1s1
Use metric measurements. Canada Post went metric in 1974.
And increasing the size of the package is normal. Small packages are easily lost in the hurlyburly of a postal terminal. Even just putting your tiny secure box is a larger poly envelope helps a lot.
The reference number and the duty and tax have nothing to do with the exporter (you). Those are for the customs people on the other end. Your buyer won't be paying any since US importers have a duty free allowance of $800.
BTW, don't be too exact about the form of the jewelry. 'Costume jewelry' is fine. You can change the prefilled description, which uses the title of your listing quite easily.