That's amazing looking lava, Glen!
I was trying to make some lava recently and I thought, at the time, that my red-stuff looked good but my black-stuff looked horrible.
I was wrong on
one of these observations!
You've nailed it with both.
If you had free rendering time to spare(and a great .tgd, like the first image shows) I'd disable the GI strength in atmosphere in the envirolight node for a big speed increase, lower the sun so it's very dark and render with huge GI detail settings 4/4 maybe. The glow should speak for itself and light up the whole surface nicely.
Excellent, I love the spattering effect.