All classes have auto-attack, you have to be in active mode and your action bar has to be "active" / selectable for you to start attacking. On durability: the information you might be reading must be outdated. Right now all items give their full benefits until they hit 0%, upon which you get no stats at all from the item.

However it does sound like you have some really weird issues. I'd say try changing the graphics settings or worst case try reinstalling and see if that fixes it.