I'd stick with AA. The 8 eVIPs and the F lounge access is a huge plus. Don't forget that OW is the only alliance that grants status-based F lounge access.
If CA works for your domestic travel, then you might want to think about banking miles with UA or some other *A carrier. 50k/yr is enough to make *G with lounge access - some *A carriers offer *G at <50k. If you do want to combine miles in one alliance, UA would be the way to go, though you won't earn as many SWUs and you may want to look into how difficult the PVG routes are for upgrading.
DL is not the carrier for international uprgades or lounge access. Getting to the forward cabin on DL involves purchasing only the most expensive Y fares and then dealing with the upgrade shenanigan lottery. The only benefit would be to have MU and CZ for mileage earning.
My advice, stick with AA and consider Priority Pass for lounge access on non-OW carriers. The domestic flights will be short anyway.