I had this dilemma myself last year. Ended up finding 2 X f seats to YVR. (We were heading for PDX). Back via Denver in J.
There's only Y seats to YVR showing at the moment so you might as well pay Rev for Y to Seattle I would think. But check all other possibilities on west coast, even Ord etc to see if other opportunities.
Good luck. I hope you find something that works.