In 1, on the ground means at the place where something happened, so the journalist is speaking directly to the victims, not speaking by phone.
In 2-5, you don't use the word "the" before "next week." So, for example, the meeting was put back until next week.
If you take out the "the", all these sentences are fine and they mean what you think: the meeting was delayed.
"Has been" and "was" mean the same thing in this usage.