As far as making it look more flare-like, you can do what RTHDRIBL does and use a much stronger brightpass for the flare generation. This gives you sharper flares without that "inverted bloom" look that several games suffer from and avoids over-flaring of bright sources on the image. Pop some streaks on top and you've got yourself a really nice flare. Maybe give some random scaling to each flare element and a color, that can help too.

On the note of RTHDRIBL, maybe read Masaki Kawase's papers if you haven't already, AFAIK he's the father of this technique and has plenty of awesome reading material (some of them are in English, others only in Japanese, but you can just translate or look at the pictures to get an idea. ) that may help to improve your results. IMO his demo is still the most impressive demo I've seen using this technique.

Of course none of this really solves the lens aperture issue but it'll still help make it look better.

PS: If you can't view the links, pop them into Google translate and set source language to Japanese and target to English. Should work.

thanks for sharing your technique - will give it a try in the near future