I can think of an alternative death for Billy that might make more sense:
He goes for the Barbasol can, the T-Rex following right behind, grabs it, and jumps into the ocean, the T-Rex narrowly missing him with a bite. However, just as he jumps, the Mosasaur (which was successfully released by Sorkin, right? I don't think they ever re-contained it.) surfaces, and he falls right into its waiting jaws
Demented, effective, would look cool, and wouldn't make Billy look so stupid.