Need some help with noob question for frenzy barb + fury ?

i'm kinda noob/newbie for the game, so I have a few questions. Currently, i'm playing offline, using the Sorc farm almost fully geared for the Frenzy barb+ Fury , but I kinda struggle a little bit with the frenzy barb ( haven't been leveling) + Fury ( also haven't been leveling).
1.i found the phys sunder, but i checked through some old posts about frenzy that i don't need it because the berserk + lawbringer. So my question is if i want to save the point in berserk do i need to use phys sunder or only Lawbringer enough for phys immune ?
2. Does Grief really need the Phase Blade 5os? it's really hard to get the 5os, and i have the superior crystal sword 5os can i use it to replace for the PB 5os ?
3. For Fury, no way i can get the cham for metamorphosis or jalal's ( drop chance way too low), what's the optional helmet? shako ? If Shako, I'm cooked cuz even my sorc uses lore + tarnhelm
4. Is the eth on the decapitator important for "Death" Fury ? and also as i know, eth weaps can't be repaired means that it's kinda suck if I'm dead.