There might indeed be cataclysmic celestial events during the trib, but the "stars" falling from heaven could be angels, too. Either way, the earth does not have to be flat for the stars to fall.Matthew 24:
29 Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken:
So - when Jesus states plainly that stars shall fall from heaven - you are just not willing to believe it?