Google thinks its algorithms are better than me at detecting false positives on my own email account, and this is enragingly false.
Now, I periodically check all my spam to catch all the false positives. I used to get extremely pissed about this, but nowadays I just allocate time every day to the task, admitting defeat.
The Google spam algorithm simply has a mind of its own, it will not listen to suggestions.
I guess my replying here is aimed at letting you know you are not alone in your frustration.
However, the algorithms are self-correcting. If the bad behavior has been corrected, you will automatically stop being spammed by Gmail after enough time has passed. As to how much time that takes: Google ain't sayin' and I have never succeeded in getting an answer from them.
Worse, people don't get why I cannot simply call someone. That's how it works in everything else.
I'd just forget it and move my mail (or the sending side thereof) to a different network, if at all possible.
Working with numerous parties to resolve some reputation issue is going to be time consuming and the whole time, you have disrupted e-mail.