My TSN refused anything but live.. even though you are against it mine liked nightcrawlers cut up and took those almost as eagerly as feeder fish, at 7 inches he now is starting to take frozen krill, and bloodworms, and whiskers the pellets his tankmates hoover down. personally i worry about getting my fish acclimated and stable in my tanks.. then wean them onto prepared foods ect. beefheart might work as well but isn't an ideal food anymore then bloodworms are imo/ime. Some fish take prepared just fine and others are finicky. I usually offer enough live foods to keep them from starveing ect.. but keep them hungry so they try other foods. My first TSN was a stubborn sob.. only ate nightcrawlers or feeder fish despite useing multiple foods and techniques, but from research and talking to other people he seemed to be the exception not the rule with these fish.
No matter how you tackle the problem I hope he starts eating for you!