Why should the USA develop a conventional ( as opposed to a neccessary small nuclear bomb) to depose the Iranian Government?
That isn't the aim of the conventional bomb in question. It's aim is to get at hardened underground sites in a variety of places all over the globe, which I think includes Korea.
You could, if you wanted to, bomb the Iran nuke sites without deposing the government in Iran. It is my opinion that B-2 would be the platform of choice, but I understand why other choices are also considered.
Why do you think this will happen within the next six weeks? What drives that timeline? Seems arbitrary.