Since Israel has not signed the treaty, no one has a legal recourse to force Israel to reveal it's nuclear secrets. If we were to "force" Israel to sign the NPT, It would be under duress. I think, legally, that would nullify the agreement. So that's a "no go" as well, unless you believe that's an acceptable way to handle treaties. I doubt you do.
I really think that it's important to stay on point here. Can we at least agree the world doesn't need any more nuclear weapons? I expect you'll agree to that, and for the moment (until you say you want more nukes), I'll presume you do. By constantly re-directing the issue from Iran to Israel, you are giving defacto acceptance to Iran obtaining nuclear weaponry, claiming Israel as an excuse. Perhaps this isn't your intent, but it still has that effect. If Israel has nukes, they have them, but what we are trying to do in the current situation is not allow a country to make any more. If we persist in going backward all the time, we'll never manage to go forward. What I propose, is that we stay on point and concentrate on Iran. By this means, we can go forward and prevent any more nuclear weapons. I think less nukes is better than more nukes, don't you?