If you use your one transcontinental flight between YVR and JFK instead of SEA-DFW-JFK you can free up a segment later, such as... LHR-YVR-JFK-BDA-MIA-SJO-DFW-HNL-SYD-AKL-MEL-PER-NRT-DEL-HKG-SIN-LHR, adding San Jose Costa Rica. Or, you could restore your BNE flight.

If you want to see more of the west coast, you can take the train affordably from Vancouver to Seattle, or there are umpteen reasonably-priced flights on Alaska Airlines and/or Virgin America between Seattle and LA/SF (or better, hire a car and drive down the coast through the Redwoods etc. to SF.)

The YVR-JFK flight is a redeye, but so is the westbound JFK-YVR, which has the disadvantage of arriving in Vancouver in the dead middle of the night.

Just some thoughts.