Hello everyone, need some clarifications about some mechanics behind pet adventures.

1. Heard some rumors that the efficiency % increases the chance of getting cards, would like to know if is true or not.
2. Read somewhere that Pure pet skill increase by 10% the chance of getting a card also considering the efficiency.
3. Does Housekeeping skill and Pure skill stack? read somewhere that the one that saves pet adventure time stacks so i wonder if the others does aswell.
4. Are cards with different colors (blue & purple) harder to obtain?
5. Do we know at what rateo the increase % of efficiency boost the item gain? Smaller upgrades of 2-3% make a noticeable difference?
6. There is an efficiency cap like 200% or something?

Need to know because got the luck to find a sohee with the event egg and had a succubus already, and soon the golden nano fish will be here taking a 3rd pet with pure skill (we don't have pet fusion yet so idk if some pet from fusion have it). Also planning to farm some armor shards and cyfar with pet adventure (playing on EU where prices for those are still very high since all the ppl is more or less at the same point in the progression and the demand is very high, reason why a triple housekeeping with decent efficiency can me amazing. And also i have a dedicated character to do pet adventures so would like to know if is worth to invest to make some cheap equip to 10/15 to boost efficiency and maybe some runes.

Thanks everyone!