Sorry, but it’s very unlikely indeed McCarthy had direct access to intelligence from Venona, though I suppose it’s possible somebody was leaking him results.
Truman himself didn’t have access to Venona, so it seems unlikely an at the time obscure senator from WI would.
Also, Venona was almost entirely from 42 to 45, with a very few as late as 48.
McCarthy was more or less right when he talked about the number and penetration of Soviet agents. It is very unlikely he had any clue who they were.
It lasted until 1980 according to Wikipedia.