Alright. Interesting post.
To begin with, I know your opponent very well. He's a good manager, a good friend and a youtuber like me. But I don't think it's his fault.
Manipulation and all those "cheats" or exploits, are allowed by the game itself, and sometimes you can say you're forced to follow them. For instance, I want to have a team around 130% at the end of the season, but at the same time, I don't want to face the two 180% teams. So in order to avoid those teams, I have to reduce my team quality somehow. I want to play against equal teams, but the draw system doesn't allow that. Is manipulation an option? No, not at all, but there's nothing else you can do.
The community has asked for an end in manipulation, tanking, upselling. I myself have wrote many reports asking for that and giving solutions. So far nothing, but I hope and I'm pretty sure something will be done this year.