Right, that’s exactly where we differ from Ginzburg and Sag’s analysis (which may or may not have been a wise move, ultimately). G&S have separate lexical entries for wh-words which are not fronted. They also have some additional pretty intricate “principles”, to make everything work for English. When we looked at that, we thought that analysis would not work for something like Russian (because of the additional principles). We also thought it would be nice to not posit additional lexical entries for wh-words. See part of the discussion here.
As for unbonunded dependeincies, in a language like Russian, both wh-arguments can be fronted, included when who said what to whom is an embedded question:
(1) Kto chto ty tochno znaesh, chto skazal?
who.NOM what.ACC 2SG definitely know.2SG that said?
"Who do you know for sure said what?" [rus]
When such wh-words are not fronted, we do need to license their position with regular head-subject and head-complement rules, and then, if none of them is fronted, with the in situ rule. Given that we also have free word order, we now have all this ambiguity, which I was able to keep more or less in check but now it turns out that maybe that was a bit too hacky.