(1) Words realise meanings — it's the stratal relation between lexicogrammar and semantics. That is, the relation is one of identity, across different levels of symbolic abstraction. See also here.
(2) 'Lexis as most delicate grammar' refers to the cline of delicacy on the lexicogrammatical stratum — the stratum of wording, not meaning. It means that, if the grammatical systems were elaborated in more detail, bundles of the most delicate features would specify individual lexical items — just as phonemes are specified by bundles of features such as {voiced, bilabial, stop}.
