[Endoperez]

1) Only a head slot, no hand slots at all.
2) Yes, by using weapon modding commands to the trident weapon. I don't think it's necessary, since the hand slots are free and the champion can just use an AoE weapon.
3) Yes, by using the magic item modding commands.

4) I don't have modding manual with me now, but you need to add a secondaryeffect weapon modding command to add AoE. I think the command for changing the type of a magic item's slot is just #type (number).

EDIT:
Oh, you're going to use it for Dom3000. In that case, you might want to use #weapon and #armor item modding commands to refer to existing Dom3000 weapon/armors.