Trying to roll up one hell of an amulet

I am attempting to make this amulet for a spectral throw marauder which will use Pillar of the Caged God and Iron Grip. My base for an amulet choice is Citrine - Dex/Str hybrid. I have a lvl 77 amulet for this. I want to try and get the best overall amulet I can. My goals for mods are:

Flaring (lvl 76) ~ x - y flat damage
Impregnable (lvl 77) ~ +x% armour
Unleashed (lvl 75) ~ +x% weapon elemental damage

Of the Titan (lvl 74) ~ +x strength
Of the Rainbow (lvl 60) ~ +x elemental resistances
Of the Infinite (lvl 77) ~ +x all attributes

Are there any different choices anyone would make here? I know the task is herculean to make this amulet, but I'm willing to try.

Lastly, question about gems, can I use Iron Grip the gem as well as Iron Grip the keystone? Will they stack?