Basically, nuclear weapon states are supposed to give non-nuclear states assistance in developing peaceful uses of nuclear technology. So, so long as Country X is a party to the treaty in good standing, others are supposed to cooperate with efforts to develop nuclear power, medicine, etc. at the lowest possible cost to that country.
In addition, non-nuclear weapon states are given various security guarantees. The NPT binds nuclear weapon states to a goal of verifyable disarmament. Further, various comminuques and UN Security Council resolutions have generally decreed that nuclear weapons states will not use nukes against non-nuclear weapon states.
As far as Pakistan, India, and Israel go, parties to the NPT are supposed to withhold any nuclear cooperation with those states. They would also not receive the same security guarantees as state parties to the NPT. That will teach them, I’m sure.