It sounds like maybe they did a conservatorship in the first place because it was quick, and, since the Tuhoys were boosters, he needed to be part of the family ASAP in order to play at Ole Miss. But while under the conservatorship, he played in the NFL, got married, bought a house, wrote a book, etc. while apparently being estranged from the Tuhoys, so it doesn't seem like a Britney Spears situation.
It also sounds like Hollywood kind of screwed everybody over. They wrote the movie as a vehicle for Sandra Bullock, so the Oher character became kind of a hapless moron who she saved and also taught to play football. So that probably sucked for Oher, once people saw the movie and assumed it was real.
According to Michael Lewis, who wrote the book, his total payout was $600,000, which he split 50/50 with the Tuhoy family. The Tuhoys split their $300,000 evenly between each family member, so that's $60,000 for Oher (which he may have declined?). Even though the movie made $300M+ and they were supposed to get 2.5% of the net profits, Hollywood accounting took care of that.
I guess the real Mrs. Tuhoy has been making money from speaking engagements, and I'm assuming no one would have any interest in listening to her if it weren't for the book/movie, so Oher may have a point there. To some extent he probably just feels like the movie ruined his life without him even getting paid for it, and he blames the Tuhoys. So that kind of sucks.