If you have the CSSU installed, you already have Matan's desktop. The desktop package in the CSSU already includes all the mods Matan's desktop gives you. (But it doesn't turn the outwardly visible ones on by default, unlike Matan's original packages may have, so most people installing the CSSU don't notice it, and, well, don't bother reading the thread/wiki enough to realize it.)

The mod that you need for what you are asking for should already work if you have the CSSU installed. (Also, you probably won't need the rotation on/off in shortcutd for long, because the CSSU keeps making portrait mode support more universal, but whatever.)

Anyway, since you have the CSSU installed, try this real quick, and if it works, I can help you get the power menu button you want. Run these in X-Term, NOT as root, but as the normal user:

This should take you to the desktop:
This should take you to the task switcher:
This should take you to the menu/launcher:
If that works, it's just a matter of adding the code you want to a button entry in /etc/systemui/systemui.xml