Hi, I understand exactly. Backups can be very frustrating. I actually have a similar backup system running on my own servers that I could easily adapt and modify (and, add a little documentation).
I would also, at your request, like to possibly comment on your proposed scheme and propose a slightly modified method using rsync (LOCALLY, not for the Ubuntu->Your Mac Setup) and possibly other if time permits.
I have been a professional system administrator for over 4 years and currently administer more servers than I can count on a daily basis, in addition to writing a heavily thorough backup system.