That's a bit difficult, modern Hinduvta, i.e the one put forward by Veer Savarkar, champions the destruction of the caste system. The most extreme Hinduvta types are VERY anti caste. Not to mention the caste system is pretty much impossible to maintain with modern technology. Discrimination...
Yeah no the Meitei and Hill tribes hate each other. They there's an ongoing outbreak of riots since just last month which has displaced 70,000+ and forced the army in to keep the peace.
I have to say that's it's unlikely that Bhutan would be able to expell non Buddhists as they'd make up about 75-80% of their population. If the British actively supported it India would probably revolt.
Religious war is a very long stretch.
However I'd disagree that English will lose it's status as the world's lingua franca. It's too late for that though I do agree Spanish and Portuguese will be more prominent than OTL
India was self sufficient in food by the late sixties. It was one of Indira's great accomplishments if not her greatest. Even with the loss of foreign imports India will come out okay. The Middle East on the other is far, far more dependent of foreign imports. Countries like the Gulf states,SA...