Added. I also split the Deathbringer's Will procs into their own group, so people who don't have the item can disable them; the macrotext to be executed is constrained to 1024 characters, so you can't include everything at the same time. :|
Also, I've noticed that the button doesn't always work on login; the keybinding is correctly set, and the button's macrotext attribute is correctly set, but it just doesn't do anything. If anyone has any ideas about this, please let me know.
I assume so, though I don't have access to any characters that can buff a ranged weapon, so I can't actually test it. I'm just putting "/click TempEnchant3 RightButton" in my button's macrotext. It works for the main hand and off hand, with TempEnchant1 and TempEnchant2. Though, if you're hiding the default temp enchant buttons, you need to call SetID on them before it will work:
if not TemporaryEnchantFrame:IsShown() then