I have a Jack Dempsey (are they the same as a Texas Cichlid?) and my roommate insisted on getting a bala shark but im going to bring him back once he gets too big.
I really havent noticed the JD nipping at my O, but you never know?!?
Unfortunately thats a texas and with that said my guess for the fin problem is nipping. That oscar stands no chance living with it, unless you got a huge tank for the O to be able to stay away, cause Texas' are rather mean fish.