Well the theory goes that Israel developed nukes and keeps it a secret because the US will stop all military aid as per the international non proliferation agreement.

Either is entirely plausible, which is what Israel wants, whatever the truth is about it. Do we have nukes? You decide. It's scary to enemies, on the one hand they get the deterrent without developing them, on the other they have them but still get US aid. 

 Yes. Either way could be the case as either way puts them in a good position, and the ambiguity makes that position even better.