Horrible looking valve seals. And how did you manage to break a valve ? 2nd , how did you manage to break a valve and NOT notice ? Geez man that sucks. I feel bad for ya - hope there isn't any damge
Putting new seals on , I like to use a deep 10mm socket and tap down the seals until they seat.
I would check the rear head as well
edit - I just re read your post. You already pulled the head and the valve hasn't fallen out yet? Now I'm confused