What's lightning-colored hair? White? Goldish? I've seen blue and even red lightning before.
The wings part and the fact he's an astronaut took me by surprise. I wasn't expecting to read either of those things.
I like Finn. Phin is too close to pin and otherwise why ruin the spelling of perfectly fine Finn?
I think you should definitely change his name from Howl--you're right, it's too obvious and if you get this published and readers immediately put it together they might draw too many parallels to the original story and yours and call you a copycat.
My vote is for Finn, most definitely. Short, spunky, fun. But capable. That's Finn.