Never used Shopify unfortunately, so I can't help you with that.
The way I tag media is using MediaElch. It requires manually going through each series and identifying it, but with your proper naming it should give decent suggestions already.
If some metadata is missing for single episodes, try changing the metadata provider, sometimes one or the other just has bad/incomplete data.
Maybe, but now I still need to remember the alias or distribute it to any machine I'm working on.
Not that difficult if you have everything managed with Ansible or similar anyways, but lots of people likely don't have that setup.