Ironically, my go-to answer for calming dinos down is "mailmen." Letting them chase and capture their own prey really calms them down and helps them burn off some energy. If that's an issue perhaps have them chase neighborhood dogs or cheetahs, if available. And, as always, make sure you put in plenty of play time! Depending on the breed, dinos need between half an hour and three hours of activity daily. Hope this helps!
In An Alternate Universe...
It's an alternate universe. Everything you post/ask is possible and true, and all the comments go with it. Don't break immersion.
The hunting drive in T-Rex is way more than some of the other breeds. Raptors for example stop being so hunt driven once they're separated from the packs. However, T-Rexes being solitary to begin with, retain the drive long after. One thing I have seen that helps is to make them think the particular 'food' is disgusting. I would recommend you build a scarecrow of sorts filled with veggies and fruit, and dress it up in a mailman uniform and let your t-rex 'hunt' it. Once he tastes the veggies, he will stop hunting the mailman. Good luck! Once the hunt drive goes down, a T-Rex is basically like a baby. Our T-Rex is never violent, even to little kids.