Try to play all notes at the same time, in the theme. Some pieces can handle the breaking, but this isn't one of them.
And why do you make an accent on the second note? I don't have the score here, so maybe I'm wrong. But is there really an accent there? In any case, the rhythm becomes disoriented, since you somewhat ignore the first beat. The second note is longer, but the first beat is still the first beat.
I wouldn't do so much of diminuendo in the end of phrases, it makes the whole theme much less singing.
And try to make it into a few long phrases. You start a new phrase after every cadence, which makes it feel very long...
I'll try to write for some variations later, but now I have to go to school! Good job so far