As far as the menus go, hold down the ALT key then click and hold the left mouse button. You will be able to drag the window around. Once you can get to the top bar, click maximize and you should be good to go.
Does your home directory have a folder named .thunderbird? Notice the dot in front of thunderbird. That's where all your mail messages, settings, etc. are. If it isn't there, try copying it from root and pasting in your home folder. You may have been logged in as root when thunderbird was installed. You could also try installing it while logged in as normal user. You have to give the root password to install but the app will be available for any user.
Hope this helps