Tell him to use the point, quote, comment strategy. Each paragraph should start with a topic sentence. I would suggest that the opening paragraph should be a summary of the historical context behind the religious intolerance. He should then move on to discuss Shylock as a character. Why has Shakespeare portrayed him in the way he has? Weave in comments about imagry and language specific to Shylock's character and actions and how this encompasses his religious beliefs. (as that is how Shakespeare has portrayed this character). Then the next section should be the same on Antonio. A section should be devoted to the final trial of shylock. What is the audience's reaction to this? What are the potential problems of staging this. He could also mention stereotping of characters - how is the stereotypical jew presented - think about Fagin, Fiddler on the Roof, etc. If he makes references to other works then that is A*.
Either as a seperate section or weaved in (if he's dyslexic it might be best as a seperate bit) discuss how audiences have changed over the ages - ie, how does a modern audience differ to the differences in religious beliefs, intolerance. Anti semitism was prevalent and acceptable then but now??? Different cultural reactions - would for example an audience in Hitler's Germany react differently to one now???
Also A* would be if he considers Shylock and/or Antonio in the role of a villain. Are They????? Compare them to Shakespeare's two main villains, Richard III and Iago in Othello. Both of these (particularly Iago) are shown to be evil and part of the dark side. Shakespeare has also had history of being interested in outsiders - think about Othello being the first black hero (albeit tragic) in English literature.
If your son goes through his notes carefully, ensures he uses point, quote, comment, includes historical and social context, makes references to various interepretations and offers in depth analysis then he should do better than a C.
I'm sorry I can't be more use - I have never taught MoV and haven't read it recently.
Good luck