Regarding Matthew 24, it would seem Jesus' predictions on Jerusalem’s ruin were fulfilled. However what of His descriptions of alterations in the sun, moon and stars? Were these fulfilled?

Biblical scholars have differing opinions on what elements of the Mount Olivet discourse relate to the destruction of the Jerusalem in 70 A.D., and what might refer to the end of the world. Some of the details quite clearly relate to the events of 70 A.D., such as wars, Jerusalem being surrounded by armies, etc. Even some other details such as earthquakes, and famines occurred around that time.
 
Other details may be references to the end of the world, (e.g. the sun and moon darkened, signs in the heavens, and the Son of Man coming on the clouds), or they may also have occurred in 70 AD. Josephus, an historian at that time, describes clouds of smoke as Jerusalem burned, which dimmed the sun and eclipsed the moon and stars. He also describes strange wonders in the heavens, possibly a comet, and strange lights near and above the Temple at night.
 
A balanced approach would be to acknowledge that all the signs had an historical reference, rooted in 70 A.D., but also symbolically point to the end of the world, of which Jerusalem is a sign.
 
As for Christ “coming on the clouds” it is a prophetic language describing judgment on ancient Israel for lack of faith. It is also clear that Jesus will come in judgment on this world as well.