Does Elders power work with Power Siphon?

Hi, new to PoE planning to build a wand+shield and spark totem shadow have a few questions thanks in advance.

In short will power siphon work with Elders power (+50% phy dmg to wand)? Say you have 100dmg on your wand does the elders first make it 150 and than power siphon take that 150 and amplify, or do you first add 50% with the siphon % bonus and apply to the base wand dmg or because siphon is an skill it ignores the passive buff on just wand and just use wands base dmg? Lastly does other passive effect on wand such as wand attack speed and dmg also work the same way with Siphon?

Relating to this and to clear up fundamental game mech about +x% phy dmg with certain weapon, does it only take the wands phy dmg part and buff that or does it take the total wands dmg (so elemental dmg also) and add x% of that total dmg as phy to the wand? (quick example 100 phy dmg 10ele dmg after 50% buff becomes 150phydmg or 155 phy dmg?) Same question with "8% increased elemental dmg" are the elemental dmg parts of the wand getting buffed 8% or is entire dmg getting buffed 8% in the form of elemental dmg.

and for skill "elemental resistance with shields" the +15% resist added is directly added to all your resist right? ie if my global lightning resist is 30% after that I get 45%. Not just boost the resists modifiers on the shield item by 15%?

Thank you so much I know I can probably find these on forum by while typing the first question a few more came to mind sorry.