>Understand strongly accented speech. I understand essentially all the “standard” French without subtitles, but very little of the Quebecois.
Most European French speakers have trouble understanding Québecois as well, especially if it delves into slang, so I wouldn't fret much. High level (and written) speech should be ok though.
>Understand very slang-heavy speech. I know a good chunk of argot but there are still plenty of informal vocab words and expressions I don’t know. Especially that damn verlan.
Again, seeing how most people over 35 don't understand any of that stuff either I wouldn't worry too much. Especially because this stuff evolves like crazy and new slang/verlan words keep popping up all the time. I'm in my late 20s and can already feel the divide in the slang I and friends in their early 20s use.
>Write error free text. I can get the message across pretty well without relying on a dictionary, but I often phrase things a bit unnaturally and make minor grammatical errors.
Like I and another poster said, most of the mistakes aren't really mistakes. Only the most extraordinary pedant would object to these.
>Quickly use less common verb tenses. While I know how to construct the past conditional and future perfect, I still can’t use them very fluidly. >Recognize all the weird literary tenses. Imperfect subjunctive? Yuck.
Yeah no one uses these. In fact if you did attempt to use these in a normal conversation there's a good chance you wouldn't be understood. Even in writing, modern authors are more and more switching to present and past perfect. Even tenses like the future are getting increasingly uncommon, people instead use the present and rely on contextual clues or markers, like in German (" we'll meet tomorrow" -> "we meet tomorrow").
What I mean to say from all of this is that even native French speakers are not completely at ease with these pain points so it's no use worrying about them too much.