If there was real legal hairsplitting going on from Thorin, as in our universe, in terms of him trying to give Bilbo nothing, the matter might have ended up in litigation, with a case such as
Bilbo Baggins, Esq. v Thorin Rex, where the hobbit sues the new King under the Mountain. I can imagine it being very difficult for Thorin to claim that the vast treasure of his grandfather just vanished.
Also, what about Bilbo being properly paid for rescuing Thorin and his people from the spiders and the Elvenkings cells?
To be fair to Thorin, he had already given Bilbo the first part of his promised reward, the mithril coat, which we later read was more valuable than the whole Shire and everything in it.
