Hi Roro,
Oddly enough, you answered your own question in your post no. 4 when you stated that you would be willing to wash someone else's feet but you couldn't sit there while they washed yours.
I'm cutting and pasting Eugene's verses:
John 13:5After that He (Jesus) poureth water into a bason, and began to wash the disciples' feet, and to wipe them with the towel wherewith he was girded.
John 13:8 Peter saith unto him, Thou shalt never wash my feet. Jesus answered him, If I wash thee not, thou hast no part with me.
John 13:9 Simon Peter saith unto him, Lord, not my feet only, but also my hands and my head.
John 13:10 Jesus saith to him, He that is washed needeth not save to wash his feet, but is clean every whit: and ye are clean, but not all (Talking of Judas). They were all saved except Judas, but their walk needed cleaned.
First, yes, washing of feet was a cultural tradition. When one had guests, they'd show up with very dusty feet, as you said in your O.P. So it would be welcoming for their host to supply water and towel so they could wash their feet and be more comfortable.
This also brings to mind Mathew 10:14. The Pharisees practiced shaking the dust off their feet as a symbolic gesture when leaving the home of an "unclean" gentile. This was a warning to them who rejected God's message.
Now to the washing of the feet at the Last Supper. This certainly means that we are to serve others as Jesus served His apostles. This is used as an example.
But did you ever think of this? John 13:8 How about the matter of being able to ACCEPT Jesus' love?
Jesus wanted to wash Peter's feet, and Peter could not accept the love Jesus offered. Peter said what you said in post 4. It's much easier to wash someone's feet instead of sitting there and letting yours be washed. It could be embarrassing, humilitating, it exposes you. But sitting there and letting Jesus do the action means accepting His love for you. Love goes beyond embarrassement, humiliation and exposure. If you accept Jesus' love these things will not bother you. Jesus told Peter that he must accept His love or Jesus would have no part of Him.
John 13:9 So Peter says okay, and agrees to the washing. He tells Jesus that He should wash not only his feet but also his hands and head. In other words, just do a complete job. But Jesus told him that since Peter was already clean (only the feet got dirty, not the whole body) he needed to have only his feet washed.
This makes me think that when we're saved we become clean - our body is washed. Then our feet get dirty and this would be when we sin, and that has to be washed by confessing our sin and being sorry for it. And then we're all clean again.
My thoughts.
Wondering