I did a quick search on google and came up with this site that provides tests that can establish a CEF level.http://examenglish.com/leveltest/index.php
The placement test can be whatever you design it to be. It’s true I was talking about it in terms of establishing a course of action but it can be used to ascertain levels as well. If you use the test in the link above and a basic placement test, I think you’ll be fine. In any case, you never find out everything there is to know about a student before actually working with them.
Definitely use materials from his workplace. Ask him to bring in things that he finds challenging, just slightly above his level. If you want ideas for using such texts, please write in again.
I can’t say about focusing on grammar or fluency: it’ll depend on what comes out of the tests and your first lesson with him. If you have enough time with him, I’d aim to brush up all his skills.