As for UA F with a connection... hmm... personally I wouldn't unless I was going to stopover in ORD - reason being I dislike internal US flights and its quite a way from ORD to SFO (plus the hassle of a transfer), unless you're on one of the planes that continues an international route domestically. I'd swap it for a ps (premium service) NYC-SFO, followed by a LHR-NYC though.
Is UA F internationally pretty crap or is it OK? I guess it wont be BA standard but given the situation its still better value that keeping the DC miles that I will lose otherwise.