I am seeing JetBlue flying nonstop from Boston-why wouldn't you just take that? Cuts out the connecting flights. That flight has you landed by 12:05 with plenty of time for the ferries.

Alternately you could consider overnighting in STT on Friday and take the first ferries on Sat. You eliminate the fear of delays and having someone making the trip alone. Flying Friday vs Saturday may also save you enough to pay for Friday nights hotel (and drinks!).