You could consider going along with the crooked look and buy a smaller pane for the right side and install two rails on different heights. The left pane will open and close normal. Hope that makes sense?

If it is in your living room is it necessary to hang a curtain from the top? You could put a decorative curtain rod lower leaving the upper part of the window uncovered and allowing in great light while still creating privacy. Or you could put up some beautiful shutters on the bottom half. If you truly want to cover the entire window you could also create a valance that could be mounted to the sophet on the right side and to the wood frame on the left side and it would hang down to cover the actual curtain rod which could be placed anywhere within the length of the valance.

You can use a ceiling mount rod, set pins so top skims soffit