Yes, I think the motif was the main inspiration for the arrangement, what chords I wanted to hear around it. I used it to build the melody and the chord progression. But when you listen to it, it can seem secondary, it's true :)
As for the ending, I tend to end on dominant chords, and I've been told that this results in an ending that doesn't feel like an ending. But I like ending that way. Come on, for you, for the next one, I'll end with a tonic chord.