[2022] Question about DoT's / ailments

Hey guys ! I need some clarification regarding DoTs:

1. Does enemy elemental resistances affect my DoT ? For example: i want to ignite by using fireball, will Flammability node (Fire resistance shred) affect damage of my ignites ?
2. How exacly aliments inflicted by minions work ?

I thought the formula is:

" base ailment damage * increased minion damage over time * increased minion damage with that ailment* increased minion ailment effectiveness"

and meanwhile i seen some guide boosting their own Frostbite Damage / applying it with minions. At least visually we have only 1 "slot" for given ailment, does it "secretly" keep track of both ailments (inflicted by me and my minions) or does it only count first hit and then keeps multiplying it - e.g. i have high Frostbite damage so i make sure i'm the one applying first hit and then my minions just multiply the amount of frostbite stacks with my damage multipliers ?

Was i wrong all my life or was that guide BS ?

edit:
3. Shock description says it substracts 5% lightning resistance, is it a flat or relative number ? e.g. if monster have 50% lightning resistsance, will i need 10 or 20 shock stacks to bring it to 0 ?