I don't see any reason to believe he's lying about any of it. He seemed genuinely disturbed by 9/11.
By helping I'm sure he meant managing or consulting some people. I doubt he did very much to get his hands physically dirty for very long, he's not that type, but that's okay. People are best used doing what they're good at.
He lives at the top of Trump Tower right? 4 miles isn't that far from way up there. While staring intently at a catastrophe I'm sure he noticed a few things falling.
Again, no reason to doubt him.