Citing unofficial translations
Citing both, as you currently have, is fine and provides good a good indication to readers who are unfamiliar with this paper.
With regards to the fact that the translation was not permitted by the author, that is strictly not your problem. Copyright doesn't apply to people who are viewing or otherwise using the copied content, but to its distributor (i.e. the translator in this case). This would be no different to me simply sharing the URL of an unofficial stream of a football match (where the official source is a payed TV channel) with a friend --  I would never get into trouble for this, only the website hosting the stream could.