I don't have a volcano, but my vape is usually set to 400F, sometimes I start at 385F for the first couple of puffs so it's not too thick vapour, but 400F does it better & tastes better to me too. I usually turn it up to 415F to finish it off & it still doesn't burn it, it can taste a bit worse at 415F though. I'm not sure all the cannabis gets to that temperature, it's more like a maximum temperature it can get to around the edges, with my vape, I don't grind it fine either or it'll block my vape up - so it needs a fairly high temperature to vape it all & it wont combust. Some cannabinoids, flavonoids, etc require a slightly higher temperature to vaporize than THC, if you prefer a purer THC high then stick to low temperatures, but if you're using it for pain relief or other medical uses then you should use a slightly higher temperature to make sure you're getting all the CBD & other stuff.
Benzene boils at 80.1 °C (176.2 °F) so I don't think you can avoid that. Naphthalene is another harmful toxin, that boils at 217.97 °C (424.35 °F), so even at 415F you shouldn't get much of that, but I wouldn't want to vape it higher than 415F even if my vape went higher, usually i stick to 400F.