Looking for the following itinerary and could use some help:

SFO>DCA
DCA>IST
IST>SIN
SIN>DPS

DPS>back to SFO

I've found availability on ANA for my dates (mid-Jan) via TKK & SQ in C for the outbound. Two questions, after not having booked one of these *A runarounds in years and perusing through the last 30 pages here:

1. Can I fly Trans-pac on the return, or do I need to retrace my steps?

2. Anyone have any ideas for more creative routings, based on recent scores? The only constants are a stopover in IST and the destination of DPS. I would be fine with more miles for an upgrade to F, but it seems like those are slim pickings around these parts these days...