4 - The "Son of Man" being seen in heaven in glory and power
I am not sure I fully understand the question tbh. I presume he was telling people that he will return and those who are fit for heaven to be with him will be gathered up.
I think it means something very different - though I am aware that lots of people would disagree with me and say the same as you!
I think Jesus is quoting from Daniel 7:13-14 where a son of man approaches the throne of God in heaven:
‘In my vision at night I looked, and there before me was one like a son of man, coming with the clouds of heaven. He approached the Ancient of Days and was led into his presence. He was given authority, glory and sovereign power; all nations and peoples of every language worshipped him. His dominion is an everlasting dominion that will not pass away, and his kingdom is one that will never be destroyed. (Daniel 7:13–14)
So Jesus is not speaking about when he will return to earth but about when he will return to heaven - from earth - and be recognised, be celebrated, be given the place of ultimate authority and power.
So this is Jesus returning to heaven after going through the cross, after resurrection and as the culmination of ascension - having completed all that His Father sent him to do. And, as Paul says in Philippians 2, being exalted by God to the highest place (Phil 2:9-11).
And from there he is reaching out and drawing people to himself - prior to his return.
For me this is hugely powerful as it reminds me that the Jesus we worship and seek to follow / serve has defeated death, has conquered sin and is in the highest place of heaven - and we are called to reign with him. It gives me some glimpse into the heavenly reality - and what Jesus continues to do on earth - which is a real source of encouragement and strength.