A couple of thoughts ...

Unless you're on the 747 ex-ATL, F to Hawaii on DL ain't much to write home about. The seats on the 767 are, as I've said in this forum a number of times, horrible, IMO. I prefer the exit rows 25, 26. Huge amounts of leg room (far more than F) and the seat is almost as wide. Meal up front is nothing special and you can buy EATS in back with all the money you saved.

If being in F is critical, have you tried to redeem miles for the whole ticket? Or maybe one ticket and buy the other in K? I mention that because, even though it's the holidays, there's a lot of capacity to Hawaii and maybe you'll get lucky. I got two tickets in F to HNL last fall for 75k per, albeit not smack in the middle of the holiday season.

Good luck.