The way you portray Kleiner is great. I love when the characterization of someone in a machinima like this can be completely changed just by the way another the protagonist reacts to them, even if all their actions are the same (that said, it's very often done really badly.)
Honestly I think it's a lot funnier when Kleiner is just low-key kind of a sociopath, not really caring about morality but still coming across as an okay guy in person. The fact that it's kind of subtle and that a regular person could totally interpret his actions as benign (while Freeman knows what the real deal is) is what makes it great. Going outright evil madman would be a little too over-the-top.
He can talk in Freeman's Mind. From the start he was saying things to people and even getting mad when they ignored him. "Freeman's Mind" is just kind of a misleading title.