2) You only roll off int if an amulet already has socket+CHD+CHC.
3) You do need to have lightning on *either* bracers or amulet, but preferably on bracers since there's no super awesome 4th stat available. The perfect amulet has CDR as fourth stat.
Usually, the best stats for amulets are (in this order): Socket, CHD, CHC, elemental damage, main stat. For the MH build the order is socket, CHD, CHC, CDR, IAS, main stat (not sure about the IAS, probably depends a lot on how much main stat you have and which build you're playing).