In our association, the lead in a 2 man game is responsible for free throw line extended from the sideline on strong side to the 3 point line on the weak side. This is contrary to the Fed manual, which, if I’m not mistaken, only extends to the lane line on the weak side. Has there been a change by the Fed on this?

They changed it a year or two ago. But you don't quite have all the details correct. THe primary only goes to the lane line on the weak side, unless the ball drops down into that lower weak side area. Then lead should come across and take that area below the ft line extended. In other words, lead isn't responsible for any off-ball activity in that weak side area, and especially not if she's got the ball on the strong side.

Not quite. The lead is responsible for off ball activity where ever it may be (including far side of the lane) when the ball is in the trail's primary. If the ball is above the FT line (perhaps near mid-court) on the lead's side, who else would there be to cover the far side of the lane?

Primary in only relevant with regards to on-ball coverage. If the ball is not in your primary, you've got EVERYTHING that is not near the ball. (speaking only about 2-man)