Good questions!
Yes, most of the searching for clues/interrogation rolls would likely be Promo- but I tried to really get players to describe HOW they were looking for clues- I had a player roll Wrestling to check under a piece of furniture for example. Sometimes you'll catch players in a specific wording and exploit it to comedic effect. "I unroll the last will and testament of the deceased" "Roll wrestling to make sure you don't rip it to shreds"
As for if you feel a roll should Succeed or Fail for the players to get what they want, that's mostly up to the GM- whatever the table would think is funnier.
Also- good call on that 3 or Lower thing, total typo. I'll update that right away. Thank you!!