If it's booked on another carrier, it wouldn't be an issue. The ticketing rule prohibition only covers cases where the back-to-back ticketing is done with both tickets on DL. I guess they might care a little if it's another carrier where DL has a revenue sharing JV, but it's not really covered by the rules. But as noted above, as a one-off itin this is not something they would look at (even if both tickets were DL) as they really only care about the habitual offenders who do this week after week. I'm still a little confused by the itins. It sounds like you are making two short trips from NYC to CCC and spending Day 3 to 14 in NYC. I suppose if these are mileage runs that makes sense. Not really sure what the point is otherwise.

Most TATL routes still have cheaper fares for Saturday night stay roundtrips, but the fare differences are pretty tame since Covid hit (particular from competitive markets like NYC). They can still be significant from less competitive markets. A mid-week trip on DTW-AMS on DL with a Sun or Mon departure and 3-day stay goes for around $1500 roundtrip. But with Thu or Fri departures on this route and same 3-day stay (giving you a Saturday night stay), the roundtrip fares are only $649 due to the cheaper Saturday night stay fares.