Why would you want leverage is a useless system like international politics?

To avoid another country invading yours, simply declare that a tactical nuke has been placed in its capital. You don't even need a weapons program to make this seem legitimate ... just say you bought it from an underpaid Russian general.

You're underestimating just how weak a rogue country is. If you tell the US that you have a nuke in DC, they won't believe you and they will crush you, overnight, with the real Special Forces. If you responsibility build your own nuclear power infrastructure, it will be assumed that you can build a bomb overnight and that's just as good as having the real thing. Japan is an example of a country with nuclear power on this level.

It doesn't work to be an enemy to the first world. They will crush you. You've gotta be a friend. That means if your country has a lot of oil, you give it to the corporations just like the powers that be want. They reward the leaders generously for going along with them and they kill you if you assert your independence and don't give them the oil. Threatening the death of civilians with nukes is just a really bad idea.

You would only counter any threats with the threat of a tactical nuke. There is no reason to declare you have them before there is a threat from another nation.

I see little reason why another country would be bothered with the enterprise before it gained momentum and wealth.

A reason to avoid nuclear power is to avoid getting attention. Avoiding oil deposits is another way to avoid attention.