Okay, Kedz, here's a quick look-see before I go to dinner:
Core temp of a fusion blast is in the millions of degrees. You can get only 3,000C if you distance yourself a bit.
http://www.bikiniatoll.com/ 'Interesting and at times infuriating details about the testing and its results on the local population. Note please the map scale - the islands are not all that large. For truly awesome destructive area you need a good asteroid impact. megaton-range nukes are merely horrifying.
Depleted uranium is mildly radioactive, unlike lead. DU rounds have long been used as anti-armor penetrators, but one notes that the kinetic-to-thermal effect of punching through armor vaporizes both armor and DU. That is quite a bit hotter than "burning," and DU rounds do not cause chain reactions as you attest.
I've never heard of a DU anchor; the concept appears silly, and I'd like a link for that factoid.
THOR is indeed a real concept, but is not operational. You'd do just as well to invoke the old ORION project and have it crash on Godzilla's head.
Speaking of which, given that Godzilla is an avid radiovore, dropping a nuke "on his head" might not even result in an explosion. The big guy needs a lot of energy to prop himself up against gravity, after all.
The "4KT" explosion you displayed is possibly an actual 4KT explosion (in its earliest stages - note the phone pole
behind the explosion). However, even the best conventional explosives suitable for use in a bomb (stability matters) are not exceptionally more powerful than good old TNT. In explosive terms, a kiloton means equivalent to 1,000 tons of TNT. Therefore, even the best conventional bomb would weigh kilotons to deliver kiloton yields.
Granted, one could merely pile that amount and lure Godzilla to it. That's been suggested before you did, of course.