Questions about HoS and DS

[pt376]

My raid 10ICC just started using DS and HOS to mitigate some damage off the Tank when we are doing Sindragosa. There are still couple of things unclear about the 2.

1. I remember seeing somewhere in Maintankadin that damage from HoS is pure physical and thus can be completely mitigated by BOP, is DS same as HoS and is pure physical damage as well?

2. Is only the physical damage mitigated or all damage mitigated?

3. Does damage reduction kick in when the damage is applied to the Tank, then 30% of what the tank takes is transferred or Damage reduction does not kick in when damage is applied to tank, 30% of the total RAW damage is transferred, damage reduction then kick when when the damage is applied to the caster?

4. How does DS and HoS stack? additive or multiplicative?

5. Does HoS and DS work with conjunction to all 3 bubble? (Alternate between Divine Shield + HoS + DS and BOP + HoS + DS maybe?)