Strengths and limitations of allegory

I am writing an essay on the British gangster film The Long Good Friday as an allegory of Thatcherism. I've done the allegorical reading, but the question specifies I assess the value and limitations of my reading. I want to say that anything that can enrich an interpretation is justification enough but I'm having trouble with this last bit. Do you have any suggestions?

I think I should assess the limitations first, then explain how to get around these limitations in order to justify my allegorical reading of the film.

P.S I have some rough notes at the bottom of the attached essay. Thank You