I’m not sure what O’s title is right now. I don’t think he is officially the POTUSE(R) until the electoral college votes for him. He resigned his Senate seat, so he’s not a Senator. I’m sure a few creative FReepers could find an appropriate acronym for his current position, though.
His 'appointments' do not have any legal standing today. After his swearing in he'll have to make it official by signing hundreds of documents. And even if the Senate 'confirms' his cabinet nominations before January 20, he still has to officialy nominate them as President and then Senate will rubber-stamp all with a quick resolution right after.