I started down the same road.... installed the Deprecated Panel Support, then use the CS6 Extension manager to change MXP's to ZXP's.
Installed eCart Successfully, but ran into an error when I moved onto Free Tools. I was trying to install in the order that I was last advised as correct installation order: eCart, FreeTools,Design Extender, DataBridge.
Haven't gone any further since running into that error... and didn't want to bug these guys since I know they are already working on this.
Happy to hear that this worked for somebody. Maybe I will try re-converting FreeTools and installing again.
Did you install ALL of these?