I realize you may have good reasons to book through united.com, but I found these sort of flights are much -lets say- easier booked through something like ctrip.
Comparing to united.com, I can normally book CA first or business through ctrip compared to economy on united.

Their fare rules are quite tolerant too; a SHA to PEK flight on CA might be fully refundable for a slightly higher cost, or something like 10% charged if refunded before flight departure, or 20% charged AFTER flight departure at the cheaper end.
There's been a few occasions where I had several return flights booked, and simply chose the one that I actually made it back to the airport for; then canceled/refunded the other[s].


Also:
Is that normal to display the fare code with BJS? BJS refers to both airports; PEK and NAY, AFAIK.