Finished it today. At first didn't like the assemblage of all the known characters on the Challenger but the really got into it, and loved it. Felt like the old-school Trek books which were about adventures and exploration and was a nice break from the more recent stuff like the Typhon Pact.
IIRC there was reference to damage being caused the size of Belgium, or something like that. A Who reference?
Not consciously - a Hitchhikers reference (though to be fair I guess Moffat was also doing a Hitchhikers reference with it), but I'll grant you there's enough DW lines bouncing around in my head that some are bound to come out even when not intended! (the same goes for the EMH getting a "very very not good" to say, left over from when he was going to be the Mark XI)
There's only one deliberate veiled DW reference in the text and so far nobody's noticed it...
ETA- I love that cat avatar...