I assume you are using the version from Github...if not, please do so.

1. Is the plugin multilingual?
The things it displays are almost all scraped from the page so will be in the page language.
But, constants entered in the admin page are used directly. If you want those different, then you will have to change the constant name, make new ones and put them in the /language/extra_defines folder.

So, if you enter japanese in the admin, it gets garbled in the plugin output somewhere?
Can you put an example of the admin text and a screenshot of the output?

3. I presume one does not need any re-writer for the product URLs.
Dunno I use CEON. I will try with a test site.