I am also having this issue... i followed the directions in the FAQ that you linked but when i am going to reinstall Avast it now states that it is already installed and to remove the previous versions... i have already looked in the library folders aka ~/Library/ApplicationSupport, ~/Library/Caches and ~/Library/LuanchAgents but there are no Avast folders to be seen... a finder search does not bring up anything either
Any guidance would be appriciated