You could start by not funding an expansionist apartheid state?
and a nuclear power who didn't sign the Treaty on the Non-Proliferation of Nuclear Weapons...
Why is that worse than a nuclear power who did, and contravened it? Not sure why you think countries should be bound by treaties they didn't sign.
Because the treaty exists to prevent the very thing Israel did - covert nuclear arms development and covert sharing of know-how ( like Israel probably did with Apartheid South Africa).
It's like criticizing a country for not being in the Paris climate accord for their environmental record/refusing to lower emissions - yeah, that's kind of the the point.