he makes many broad statements and then carves away caveats

Which makes his thesis kinda hard to pin down, doesn't it? So what precise, hard, falsifiable statements about the nature of value of a good does Marx make, you think?

the actual theory is inoffensive as a "dollar theory of price," in which the 'price' of a commodity is the 'number of dollars it costs'

That's not inoffensive at all. There is a great divide between thinking the value comes from the supply side and thinking the value comes from the demand side. The theory is inoffensive if you make it say nothing useful, but that's not how it has been read.

Marx stayed in the motte

Did he now? You think he didn't make any connections between the LTV and his characterization of the bourgeoisie as parasites inasmuch all the value is created by the labour of the workers?