You talk a lot about the two witnesses, but it seems that you don't understand who sent them nor what it means for them to go up to heaven in a cloud.
Rev 11:3 And I will grant authority to my two witnesses, and they will prophesy for 1,260 days, clothed in sackcloth.”
Rev 11:4 These are the two olive trees and the two lampstands that stand before the Lord of the earth.
Rev 11:5 And if anyone would harm them, fire pours from their mouth and consumes their foes. If anyone would harm them, this is how he is doomed to be killed.
Rev 11:6 They have the power to shut the sky, that no rain may fall during the days of their prophesying, and they have power over the waters to turn them into blood and to strike the earth with every kind of plague, as often as they desire.
Rev 11:7 And when they have finished their testimony, the beast that rises from the bottomless pit will make war on them and conquer them and kill them,
Rev 11:8 and their dead bodies will lie in the street of the great city that symbolically is called Sodom and Egypt, where their Lord was crucified.
Rev 11:9 For three and a half days some from the peoples and tribes and languages and nations will gaze at their dead bodies and refuse to let them be placed in a tomb,
Rev 11:10 and those who dwell on the earth will rejoice over them and make merry and exchange presents, because these two prophets had been a torment to those who dwell on the earth.
Rev 11:11 But after the three and a half days a breath of life from God entered them, and they stood up on their feet, and great fear fell on those who saw them.
Rev 11:12 Then they heard a loud voice from heaven saying to them, “Come up here!” And they went up to heaven in a cloud, and their enemies watched them. (ESV)
It is the voice from heaven (Rev 10), the voice of God, that says the two witnesses are his. That means, the witnesses are God's witnesses, prophesying on his behalf. The beast kills them, which again shows that they belong to God. God breathes life into them three and a half days later and then calls them up to heaven, and they go up to heaven in a cloud. It's all fairly straight forward.
As for the cloud, it is reminiscent of Jesus's ascension:
Act 1:9 And when he had said these things, as they were looking on, he was lifted up, and a cloud took him out of their sight. (ESV)
There is nothing to suggest that it has anything to do with a nuclear bomb.