some comments on your three questions/

on 1st: This is a bug. From_checkbox should use the value parameter just a you suggested it.
on 2nd: Arg... The array_flip-issue again... Urgs... We have to refactor this in the next release.
on 3rd: I already adjusted you js-code to:

from misc.js

    $("body.taskNoteOnPersonEdit input#new_project").change(function(e)
    {
		$('#proj').toggle();
		$('#proj_list').toggle();
    });

As you can see, with jquery you can write javascript code much shorter.

some comments on your three questions / #2633