What folders should I backup to my computer
Your SD card contains pretty much all the data you need.

In addition to app backup, you can also use SMS Backup+ to backup your texts to the SD card (and then to the home server).

Titanium Backup Pro version has an option to backup files to your Dropbox folder, so you can use that instead of rsync if you like.

Also, try to move as much data to the cloud as you can - including contacts, settings, photos etc - you get peace of mind knowing that most things are already backed up even if your phone gets damaged or stolen.