OP doesn't appear to have status so would have to pay extra for E+. And wants to be in SFO around 7p so 7a UA nonstop is not good. AC nonstop later in the day is better than connecting through either IAD or DEN, both are pretty miserable terminals to spend any time at.

As others have suggested, use CO site. Set up status match/CO account and transfer miles to CO, or just find the flight on the CO site and call UA to book. Just put in your cities to the normal flight search and check off "Award", then do the search. It will list all the available flights as non stops and connections, first CO and UA, but also AC.