While they may have tube launched Harpoon missiles(not nukes)...they also have home-grown cruise missiles which are tube launched.
Each boat is capable of APPROXIMATELY 12 single-warhead missiles of moderate weight...25-50KT. The actual numbers are held very, very close.
Less is known about the Israeli arsenal than any other in the world.
I don’t know how much of your information is correct.
As far as I know and from some research I’ve done with Google the deal is as follows:
Some sources say the Israeli SLCM may be called the “Popeye Turbo”. Some say it is an enlarged version of the Israeli “Gabriel 4LR”. Yet others say it is an entirely different type of cruise missile of completely unique design.
Maximum range of the SLCM is estimated to be as much as 2,400km, putting it in the Tomahawk range (2,500km).
The SLCM is fired from one of four large 25.5 inch tubes.
Nuclear warhead size on each SLCM is estimated to be between 300-400 Kilotons which is close to a single W88 (475Kt) warhead on our Trident II.
As far as how many SLCMs each sub can carry, it is unknown. Where did you get the 12 missiles number from?
All that being said, all I’ve posted above may be mere conjecture, precisely because, as you said, very little ACTUAL data is known about the Israeli nuke program and their subs.