Jazz chords layout question

[Jacques Menu]

Hello folks,

I’m trying to setup the attached example as in the following, with an added 
staff containing empty measures as an exercise score:

What I currently get is:

Questions:
        - why do the marks appear without a box around them?
        - why does \repeat percent not produce percent signs?
        - how can I get the measures to be equal length?
        - how can I ‘push’ the beginning of the seconda volta to the middle of 
the line?

Thanks for your help!

JM

TakeTheATrainWorkScoreWithRepeats.ly
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