I can't believe that someone I had helped and supported would steal from me. It's 'a' real 'stab in the back'.
They don't really know how much the work will cost. They're just taking 'a stab' [='shot'] 'in the dark'.
He 'stabbed' the piece of meat with a fork. = He 'stabbed' the fork into the piece of meat.
(..) Well, I thought you were. So now you gotta buy me dinner. Maybe you can shoot someone and then see me professionally. I'll stab someone in the heart with a fucking ice pick if it gets me dinner with you. That's all right. I'm a detective. I'll find you. No, sorry. I'm just joking. (..)2006 The Departed