Mujitsu and Tairaku's Shakuhachi BBQ

All ready read a lot on this forum about repairing a cracked bamboo, but I would like some advice concerning a damaged ji in the bore, and how to tighten well the bindings.

First part and rarest to my knowlede, I have a rather old and nice signed kinko jiari, around 50/60 years of age. Inside the bore there is a special thing that looks like an anomaly, or may be it is a special shape to help the air into the bore: under the utaguchi, at around 2cm from top, start two litlle walls, very thin lines around 7cm lenght, that are 1mm high and wide, not really straight, but quite symetrical, each at one edge of the utaguchi. It looks like when laquer messes when drying on a wall and makes shapes, but it is rather the ji that moved at some point in the flute life. Now, it just happened one little part cracked and falled after an inspection with the finger, and now the cleaning cloth took another away, showing the whitness of ji and the urushi is strating to crack too at that place in the bore. So, the lines are made of ji, strange, as it must happened after the hassun left the maker shop, well inspected, except if he made it purposely.
My interrogation, can I attemps to take those two lines away -some said no, some yes (sanding them and laquer the area) or are they part of the making of the bore, and will that change the behavior of the flute? Not quite sure as the lines look rather an incident in a drying process. And it lived like this so many years.
Has anyone seen these kind of relief, when the rest of the bore is neat and well polished?

Second part, as it cracked at the upper part, I would like one trick to keep the tightness of a binding at the moment you cut the line, and pass the end in the knot, before pulling the two ends. It is at that time that some tightness is lost. I orderd 65 lbs test line, as my 22lbs monofilament is letting the crack open again. Any trick (besides having 4 hands)? Was thinking to use big clamps to keep the tightness before cuting the line, but not seems appropriate. Some hint from those who master that art?
Thank you
Dominique