Have you heard of dark matter? All it takes for night is to block light.
Jesus came with power at His resurrection, and was seen by over 500 people. The church was initiated with power of the Day of Pentecost.
Those Jews who have not yet returned to Israel are those who are satisfied with their lives and are not seeking God with their whole heart. I worked for such Jews for 23 years. Most American Jews are far from Orthodox in their beliefs. The Israel that Jesus will reign over as King will extend from the Euphrates River to the River of Egypt, which is more than enough real estate to contain all the Jew's.
As to praying to cast a mountain into the sea, for what purpose? To try to convince a skeptic? If you think God will answer that type of prayer then why don't you try it, since I don't have a compelling reason to do so. I think praying for AIDS victims in Africa is a better use of prayer. Also Jesus used that as an example of the power of prayer, not as something we should pray for.
Yes, the Jews are still waiting for the Conquering Messiah who will reign with the Key of David from Jerusalem. The Messianic prophesies concerning the Conquering Messiah are yet to be fulfilled.