Lolth looks older, more haggard, after the 'death star'-attack. Is she losing control of her form, or is it 'just' the massive beating she's taking?
That tri-beam attack looked seriously meaty, i think that one put a serious dent in Lolth's strength, it hurled her up in the air and forced her to retreat, so i'd say it's a little of column a and a little of column b.
As for the Beholder King: Aberrations are just that; aberrant. Their internal physiology is different to that of humanoids and animals. The King's crucial organs may be spread out through his whole body as a series of webs, rather than compact nodes.
Beholder organs are actually surprisingly straight forward (if incredibly alien), the only really genuinely aberrant thing about Beholder internals is the fact that they just ignore gravity for no reason.
A Beholder's 'head' is actually mostly filled with mouth and digestive tract, unless you happen to hit the point just behind the main eyeball (where the brain and 'lungs' are, beholders don't have a heart) you can actually poke holes in a Beholder all day and none of them will be immediately fatal.
Given the fact that the Beholder King has at least enough power to go toe to toe with an avatar of a major deity and come out on top in the first round, I'm sure he has the power neccessary to heal himself up from any not immediately fatal wounds. It also wouldn't be too surprising if he had some kind of fast healing or regeneration too.