Esaias, in my opinion your commentary about Matt 18 did great until you got to the verse in question. Jesus is merely saying that if two or three do something IN HIS NAME, it's like Him personally being there. he is represented as being there in those two or three. It's not saying He is present Himself, since that is redundant. He is everywhere anyway, and He indwells us all anyway as well. But the reason that which is bound or loosed in earth is also so in heaven is because those in earth who do this in his name are AS GOOD AS HIMSELF being there and having done it. Its is not saying two or three can gather and He will bless us with His presence. For that matter, we can be alone and He is with us!
It is speaking in terms of proxy, He is in our midst by proxy if we do this in His way and in His name.
Paul said the same thing!
1 Corinthians 5:3-5 For I verily, as absent in body, but present in spirit, have judged already, as though I were present, concerning him that hath so done this deed, (4) In the name of our Lord Jesus Christ, when ye are gathered together, and my spirit, with the power of our Lord Jesus Christ, (5) To deliver such an one unto Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.
The power of Jesus is His authority, and that is what it means to do things in His name. It's putting us in the place of Jesus by proxy. We're doing this in His authority, and not our own.
When a policeman commands somebody to do something in the name of the Law, the law is not physically there except in the person of that officer. That is what Jesus mean by two or three gathering in His name and Him being present. By proxy.