1. They're always very close to spec or over. You can ask them to test it for you before they ship it out, just contact Susie at firstname.lastname@example.org
2. No. Not on this particular model.
4. Metal, decent to good quality. It'll most likely last ya. And if you want to make sure, buy 2 (still less than a DL laser) so you have another just in case one breaks (there's a warranty and chances are it won't break from casual use, though).