The only reason **** wants these mini-nukes is so he can use them. The warheads in the existing arsenal are just too big to use without causing a massive international incident, and most likely a Third World War. He figures that if he can get nukes down to a very small size, then he can use them without fear of reprisals from any country. Also, don't forget that a helluva lot of this money will go to big defence contractors (eg Lockheed Martin), who built the US's Cold War-era tactical and strategic delivery systems (eg Minuteman ICBMs IIRC). These corporations make large donations to the political parties...
Personally, I think he's got weapons that can do a similar level of damage already. Large fuel-air warheads would be perfectly suited to this kind of attack (IIRC, this type of weapon was used in the Afghan mountains), and they don't have the stigma of nuclear weapons.
Also, as has been said, as soon as **** uses any form of nuke, it'll be open season. It won't be long before somebody breaks out the multi-megatonnes...