Ok answering my own question- called Hainan’s China Contact #. Jumped through a couple hoops, talked to a live agent and finally got my eticket number using Partner Confirmation PNR and was able to do seat selection. Yeah!

Had to use my broken Mandarin though. They kept wanting to transfer me to Hainans mileage club center and I had to make it clear that I used Alaska Mileage for the ticket.

Bonus: was told I’d get a free hotel overnight since it’s a forced overnight connection to domestic leg to Shanghai!

I didn’t bother calling their US line since it’s currently closed.