I think it's possible for a building not to be obliterated though near a large explosion. The number of factors involved is immense, and the system is chaotic as it nearly always is. Rare, unexpected, and paradoxical things do happen.
It's not some sort of law of nature that a "nuclear" bomb would have destroyed that building; it's no a priori truth. Without that status it seems to me that the notion that it's "...clear 100% proof..." is far overblown. Sure you could take it as a bit of evidence, it might even be somewhat persuasive, but it's not an open and shut case unless that building not being obliterated is a necessary and sufficient condition to prove a "nuclear" bomb was not dropped.
That this is all the 'proof' one would need seems a bit of a stretch to me, to say the least.
Also thank you for your kind words.
You are never lost for words it seems..
Facts, evidence, coherent points of view...but never words!