Buddy, try to avoid physics. MS in physics people are often left depressed after sitting the 'ruthless' physics exam. You have to have broad+in-depth+detailed knowledge on the syllabus in physics.

Therefore, IR is clearly a better choice - Your current Affairs study will guide you in this subject matter. It is interesting, rewarding and can catch you some good marks. (Paired well with Intl Law)

Over that, go for Public Administration. Takes less time to cover, straightforward syllabus, lots of material available + will help you understand the civil system & bureaucracy.

Good Luck.

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"He who has a why to live for, can bear almost any how." (Friedrich Nietzsche)