Beginner's question: breathe marks only in lower voice

Hi, I am just starting out with lilypond. I am setting a ChoirStaff score, and I would like to be able to set breahemarks on the lower voice on the treble staff only, but they appear at the top even is written in the lower voice. Is there a trick how I can restrict them to the lower voice? ___

note extension dot positioning

How can I avoid lilypond placing the extension dot for the note of the upper voice behind the lower voice note? I'd like to have the upper voice note (including dot) to the left (or right) of the lower voice note, and its dot should be next to the note. see attached screenshot <>_