How to get Content Filter lists

That would certainly be an option yes, then you could use the snippet above to extract the list into a machine readable format and have it there to use in FreeMarker, just don't forget to update it if you update the list. You could also use a custom content field for the same purpose, just note that both, custom settings and custom content fields are length limited (I think 10000 characters by default, but don't quote me on that), so if your list is particularly long you might have to ask for a higher character limit for your custom setting.