But the dude actually says 'I can't open up the tubes, this tech's too old for me, I might kill the person inside' and then five minutes later he's the mack daddy of cryotube shenanigans.
As for Khan's blood, the crew were augments, just like him. IIRC Bones says that they can't thaw anyone else out to check because he can't work the tubes, but then he takes someone out just to put Kirk in so why didn't he check their blood then? Yeah, there's no guarantee that their blood would be the same, but how did Khan even know that his blood had that sort of property anyway? Did they tell him he had blood type O-Magical down at the Federation blood bank?
God, what a shit film STID is. But there's lots of 'splosions and Spock flying into a nerd rage and pummelling someone with his fists (for the third time in two films, how original), so there's that.
New Khan knew he had O-Magical the same way Old Khan knew Chekhov.