That's right dude. It makes "movie sense", but as you say, when he ad-libs, it tends to go sidewards. PJ is not someone I would expect to make "his own movies" (wanna see his own work, watch meet the feebles) He IS however very good at adapting a story to the screen, he can "translate" well. (which is a laudable skill all its own, but it is NOT the same as creating your own source material).
It was, but PJ was setting up his own "legacy weapon" and the way they built up Smaug (as a now ancient Wyrm, rather than still an adult), a bow just would not cut it anymore.
Yup, Men make their own fate in M-E, whereas the Elves, the dwarves and the Wizards are tied to a far older fate *that they are aware of* Hobbits have even more free will.
It's expressed via Tauriel, (Legolas' Girlfriend) rather than Thranduil in the movie, she is the one who still has a sense of wonder for the world, which is why she get Legolas in to help the dwarves (though she couches it as hunting the orc invaders instead of helping the Dwarves directly). So, the interest is still there, just expressed via a different character and given a "forbidden elf/dwarf love" makeover. (to be fair it's not really "love" more a mutual fascination with opposing views/lives)
Anyway, go see it dude, you will like it about 80%, same as I did I think