Not a bad run for the money. I have a SIN trip planned for the same weekend. It is 9200+ miles each way. I'm going the following:
ONT-LAX
LAX-NRT
NRT-SIN
SIN-NRT
NRT-LAX
LAX-ONT
All but ONT-LAX,LAX-ONT (approx 48 airmiles) in UA business.
If you're going in NW coach, it could be a long & tiring ride. (tight pitch compared to E+ & MRTC). Bearable in Business. Price decent on your fares.
I did 3 SIN trips last year in coach. Coach is survivable.