I haven't tried PA12, but most of the internet info I see recommends 240 - 275º. I'd try the low end of the range first in case swelling in the tube is an issue. The bore of the tube is 2.0mm. I might also try using the PTFE hot end, with the understanding that the tube might need to be changed occasionally.
Sorry about your customs experience - how is nearly 100% duty even possible? That's outrageous. The value and HS code of the goods was correctly indicated on the customs form.