With that much United metal, it seems like you'd be best off crediting to United and earning UA status. Assuming a lot of your travels are J/P/Z type fares, you wouldn't need any shortcuts to faster *G status...

There's no real way to "consolidate" anything (short of converting miles and losing a ton of value). But you could certainly hold off on redeeming your other *A miles until you have United Gold, which you would pretty quickly after a couple of your EDI-SFO R/T's.

Airlines don't usually status-match within the alliance, but if all of your UA is in some sort of business class fare this isn't really an issue.

I don't know Singapore's program *real* well. If someone has a case for earning there since that's where the existing status is, I'd be interested in hearing it.