Pakistan's second nuclear test in 1998 was 25 kilotonnes at maximum, according to your own calculations. American Physics Society estimated only 8 kilotonnes. I agree with your own estimate though.
Did 50 mega-tonne Tsar bomb cause a nuclear winter? You do realize that a 50 mega-tonne bomb releases the energy of 1000 bombs each equal to 50 kilotonnes. Right?
Let's assume that India detonates a 100 kilotonne bomb over the city of Mand (which seems to be the closest city to Iran's border). Even then, radiation radius, thermal radiation radius and blast damage radius will all fall short of reaching Iranian cities. Again, if India and Pakistan really want to nuke the crap out of each other, feel free to do so. Nobody cares really and it will only cause human tragedy for your nations unfortunately. We may not even need to distribute iodine pills, but we may do it as a safety measure.