IMO, he needs to be more like he was from the last debate when answering his electibility question. Pen in hand, making his point known in laymens terms ("so.. we borrow 10billion from chine, give it to .... " was just brilliant) and literally schooling/teaching the other candidates and the audience in an assertive manner.
Theres no need to be angry for the sake of being angry. People already think he is an "angry old man" .
What he needs to do is be assertive and then add a touch of hope to his debate-form message.Tell the audience how much better it would be with his policies and how they will benefit. Paint a picture of prosperity and freedom , rather than just being negative about the current climate, as important as it is to make people aware of.