No, it is not right.  I don't think you can rationalize to yourself (or to your client) this is what he/she has for foreign currency gain.  You may like to do a bit more research.

For NIIT, the answer you need is right in the regs for 1411.

As for the answer to your question about monthly payment, it's in my original response and the threads I cited.  You don't seem to have read these before responding.