Gino,

I do believe the Son's wedding or marriage in Matthew 22 is the marriage supper of the Lamb because the servants of the King in Matthew 22:4 are to tell those who are bidden to the wedding, "Behold, I have prepared my dinner: my oxen and fatlings are killed, and all things are ready: come unto the marriage."

As for where the marriage supper takes place, you made an excellent point that the man who had no wedding garment wouldn't be able to get into heaven if the marriage supper takes place in heaven.  That would be due to the fact that he wouldn't receive an immortal body when the rapture/resurrection event takes place in order to go with Jesus to heaven.

However, please consider the fact that the same man with no wedding garment would not be able to get inside the city of New Jerusalem when it comes down from heaven if the marriage supper takes place inside of it because Revelation  21:27 says, "And there shall in no wise enter into it any thing that defileth, neither whatsoever worketh abomination, or maketh a lie: but they which are written in the Lamb's book of life."  Don't forget New Jerusalem is surrounded by a wall and had twelve gates with twelve angels at the gates so it is very secure.

Matthew 22 is a parable so in my opinion the man without a wedding garment who is bound hand and foot and cast into outer darkness who is weeping and gnashing his teeth is comparable to being a prisoner (bound hands and feet who can't escape) who is trapped on the outer earth in a great spiritual darkness when Satan and his fallen angels are on Earth.  He's weeping and gnashing his teeth because he missed being in the rapture/resurrection event.