Smyth being a daughter county of Wythe, I imagine there'd be a connection. At the same time there was quite a _lot_ of Pickles in the area (checking with the 1790-1860 census records and tax lists etc). It's going to be difficult sorting them out.
Actually you're probably right about Polly Porter being his second wife. Interestingly enough a sort of half-cousin of ours (from Polly's first marriage), Steve Gose, was active in the oil bidness here in Texas back during the early 1950s; don't know what became of him.