Michael Dorn just walked on set.This film offers no explanation for why Worf is in it. He literally just shows up and they go with it. My guess: Michael Dorn initially refused to do the film, but got lost on his way to the set of DS9 and happened to walk into Patrick Stewart while filming that corridor scene in the opening. Why waste such a good take when you can just throw him in.
There was supposed to be a Goose That Laid The Golden Egg metaphor that got lost somewhere in the movieDestroying the planet would likely have killed whatever it was that made it so rejuvenating (or reduced it to a comparative short term effect).
There is another way to harness the radiation without destroying the Ba'ku homeworldThe Enterprise crew starts to feel the effects of the radiation the MINUTE they enter the Briar Patch, and Picard even says that it's all over the region. Dougherty just didn't want to wait to find it.