(2) It'll automatically be in 3.5 approximately the end of this year. It will probably also be backported into the next 3.4.x, but I can't comment on schedules either for that or for the "downstream" Red Hat Storage releases.
(3) I don't know of any such instructions off the top of my head. Basically you'll have to edit /etc/glusterfs/glusterd.vol and add by hand the same auth options that are available for volumes via the CLI. I think there are (possibly hidden) CLI options that you'd need to specify username/password to work with that. If you try it and things aren't seeming fairly obvious, feel free to ping me via email (jdarcy@myemployer.com) or Freenode IRC.