The log is exactly what I expected to see: a partly updated system. You need to remove the older expl3 bundle and install l3kernel. You may also need ot remove the older xpackage bundle and replace with the newer l3packages. From the Terminal, sudo tlmgr update --self --all will do this.
As both Debian maintainer of TeX Live and author of tlmgr, I would like to state my personal ideas about it:
First, with the Debian native packages of TeX Live there will be in foreseeable time no tlmgr available. Even if it will be available, then only for managing TEXMFHOME or TEXMFLOCAL (for the sysadmin) (by using the user mode patches for tlmgr which are badly outdated at the moment).
On the other hand, it might not be necessary to have tlmgr available. Package installation, removal and configuration is done by the APT family (apt-get, aptitude and respective GUIs). Package search can be done with apt-cache search. That leads to the following suggestions:
For normal users, that are users who are not developers of (La)TeX/Font/etc packages, nor play with the latest font developments (esp. otf math fonts), for these users it is better on Debian/Ubuntu to stay with the native packages instead of installing your own copy. Especially if one does not know exactly about basic sysadmin tasks (PATH search priority, permissions etc), since if you don't know it is bound to create problems.
If you are developer, or have experience enough with both basic sysadmin tasks, using TeX Live upstream together with either a proper equivs package for texlive, or (disk space allowing) double installation.
Furthermore, if you are using Debian testing or sid (and if it exists something similar in Ubuntu), then after release of wheezy I plan to do monthly updates of the texlive packages based on the current tlnet status. Thus even Debian people would come - with a short delay - to latest packages.
Best Answer
As far as I know, TeX Live doesn't install TeXworks on GNU/Linux systems, because it would be too difficult to cope with dependencies on the various distributions. You can find a packaged version at
https://admin.fedoraproject.org/pkgdb/applications/Texworks/