Hi,
Our Japanese staff is currently in vacation so I'll answer instead in English (I can read and write Japanese but my English is way better).
Regarding the address_street2 field, if you want to translate it, you can simply add such line in the translation override area of your languages:
STREET2="Street (additional info)"
Regarding the order invoice id reset option, that option will reset the invoice id, not the invoice number. If you don't use the invoice id in the invoice number you won't see the difference. So it actually depends on the invoice number format that you're using.