By 150 B.C., the Greek astronomer Eratosthenes had already measured the 25,000-mile circumference of the earth. The round shape of our planet was a conclusion easily drawn by watching ships disappear over the horizon and also by observing eclipse shadows, and we can assume that such information was well known to New Testament writers. Earth's spherical shape was, of course, also understood by Christopher Columbus.
Which is true, but is irrelevant regarding the Bible. As I noted in post 590, the text, as a whole, is consistent with the view held in that part of the world contemporaneously with the time the Old Testament was written (i.e., the earth as a flat disk or rectangular shape, surrounded by ocean, capped with a canopy ("vault") of sky on which the sun, moon, planets and stars traversed.) This is inconsistent with anything approaching a modern cosmology.
If you want biblical discussion on the shape of the earth, and the motion of the earth and planets, you have to go to the oldest writings:
The epistles of Enoch. There is considerable description therein, and it is all in keeping with the current general understanding of the solar system.
As to whether the earth hangs on nothing, it definately appears to hang on nothing, and to that extent, the description in Job is accurate for the purpose of the statement, and the context thereof.