I am not a CSP. If you find my answer helpful take it otherwise just ignore it and accept my apology for that. Coming to your queries in preceeding words.

As far as combination is concerned that is okay only when you feel comfortable. Just an opinion, Public Ad seems to be odd in this combination. You asked about including International Law. It will be better if you replace Public Ad with International Law. As per your words International Law will help you out in International relations as well. That is true. In syllabus of International Relations one can see a sub topic named "International Law". Furthermore you know about your own taste. As far as it is concerned that how much time it will take. Just keep one thing in mind never let other's opinion be your destiny. If Ahmed says International Relations should be completed within 10 days. Does that really hold any weight? The answer would be in negative. Make your own plans and work on them. You know your strengths and weaknesses. Draw a road to destiny for yourself. If you are going for CE2017, keep time duration in mind, let books be beauty of libraries or bookstore. Grab a laptop and do topic wise study online. Work smartly, that means do topicwise study and to the point. You can find ample data on internet on each subject. Provide your email for material in soft.

This is just my humble opinion. This is what I think. Further if my reply is not helpful kindly ignore it.

Regards.

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Talib-e-Dua