You suggested that perhaps the correct Greek word (in John 14:16) should have been “pariklutos” rather than “paracletos”. We have close to 6000 Greek manuscripts of the Gospel of John and every last one says “paracletos”, “comforter” or “counselor” and not one of them says the Greek word that you say should possibly be there. So 100% of the manuscripts we have agree with our interpretation, not your interpretation.
You suggested that since the Holy Spirit has always been here with them when Jesus says that the comforter is coming, it can’t refer to the Holy Spirit. But if we actually read the passage in context, Jesus’ meaning is entirely clear. Jesus says in John 14:15 “If you love me, you will keep my commandments. I will ask the Father and He will give you another helper that he may be with you forever.” Jesus is talking to his disciples (the disciples that he has been walking with) and he says “The father will give you another helper that he may be with you forever.” If Muhammad was with Jesus’ disciples and with them forever, I would like you to explain in what sense this was the case. “That is the Spirit of truth”. So he identifies the being he’s talking about as the Spirit of Truth, whom the world cannot receive because it does not see him (so this being is not visible). Muhammad was visible, so please explain what this means because “it does not see him”. Furthermore, “or know him but you know him because he abides with you”. The being, the comforter already was abiding with Jesus’ followers. If this refers to Muhammad, please explain to us in what sense Muhammad was abiding with Jesus’ disciples and “will be in you”. What Jesus says is: Because he abides with you, the Spirit is already here. The difference is that he is going to be in you. So the change that is coming is not that suddenly this comforter, who was not here before, is going to appear. It’s that the Spirit, that was with them, was now going to dwell in them. This refers to what Christians believe about the Holy Spirit perfectly. The Spirit was already with the disciples but because of Jesus’ sacrifice on the cross, the Spirit was now going to be able to indwell the disciples, Jesus’ followers in a very new sense and be with us forever. In context, every single criterion that is given of the coming comforter fits our interpretation of the Holy Spirit and not one of these fits with the interpretation that this refers to Muhammad.