(1) I've given up on symlinks, I open several editor windows instead.
Have you considered using symlinks the other way round? I.e having a folder containing all the files you want in your "project" which would be opened in Textmate, and then setup symlinks to point back to it from other locations on the disk.
In theory this would provide many benefits (i.e. grouping all the files in one place, allowing for one version control repo for them all, one .tm_properties file, etc...).
Of course, if other applications which need to use the files in their "distributed form" don't follow symlinks, you have a problem!
D.