won't idle below 1000rpm after rod and jet change

If I had a vacuum leak, wouldn't that mean I should see a fluctuation in the vacuum gauge reading?

No, in fact the early AFBs that had the great big idle speed screw in the middle essentially WAS a controllable vacuum leak!!! You moved the screw, which let in more air, adjusted the mixture screws, and "walked" back and forth until you got what you wanted

Like this'n