all the good Nazis would have been in Berlin, and that bomb probably would've taken out almost all of the Nazi High Command, including der Furhrer. Probably the end of the war.
This is a very unlikely event. Central european cities simply aren´s build like japanese. If You compare the damage to buildings with the distance to point zero, You can analyse the blast effect of the then in use bombs dropped on Nagasaki and Hieroshima. The high degree of area destruction caused by them is to a very large extent attributable to the light, wooden construction of buildings in both japanese cities. Beton, stone and brick constructions usually prevailed in Japan. Damage was generally caused above the surface and damage below the surface was limited instead.
The large european cities not only are build from very thick and solid stone walls but also regularely have cellars for shelters.
In addition to this, Flakbunkers of the period placed on the larger cities are proof against blast, heat effects and radiation. They do have their own electrical plants and ressources. The subway system would also offer a degree of protection depending on distance to point zero.
This all is nothing in comparison to the autark Führerbunker substructures where the nazi elite housed during the latter part of the war. Don´t expect the nazi leadership to be taken out by a nuke unless the nuke happens to hit the bunker physically.
If there were a possibility of a Nazi counter nuclear strike, say against London, then I imagine the British wouldn't have been so keen on a nuclear strike on Berlin. However, the U.S. might have just gone ahead and done it anyway without British approval (or knowledge). Who knows - thankfully it never came to that.
Yes, thankfully. They were in possession a more dangerous substance than a nuke. Had they been nuked, they may have used their refined Botulinum against the UK and likely also against the US East coats with millions of losses on human life. The UK may have used it´s stocks of nerve gas in return, causing millions of losses in europe. Anyhow, these are bitter prospects.