Who cares about the ozone layer. Even a limited nuclear war between India and Pakistan would kill millions of people.
On the bright side, phone tech support would improve.
Perhaps 3-6. Each.
The two countries really only need two. Each.
If each has one, the two are in a propaganda war = Unstable.
If each has two, then the region is stable. Neither can attack the other first and be absolutely positively sure it will not be attacked in return.
But nothing - ever! - has suggested either country has made more than 5 weapons. Except this story.