Would a foreign ff program number hurt precheck odds?
Shouldn't make a difference what FF number you use. The data that goes to the TSA doesn't include that, forget everything exactly but it's travelers full name, gender, and DOB for sure. The TSA then decides if one gets pre-check or not. Airline has no say in this.
Those FFers that were bring invites to try pre-check were having their data sent to be considered, vs. other flyers who weren't being considered, IIRC.