I'd break the edges without hesitation. Had to do that on all my MP moulds for the same reasons you outlined.
As for #1 or #2 the difference besides capacity is #1 is 2 1/4" and #2 is 2 1/2" across the top. Thanks for the additional information and guidance. I normally learn things of this nature the "less than easy way" myself.My threading die came from Ace, and it was perhaps $7.00 or so. Now I wonder if my ladle is a #1 instead of a #2. My shaft size is .25, and I used a 1/4-28 die. When you install your handle, run it down until the rod bottoms out, then back it off a turn or two before tightening. I doubt we'd see an issue with it being in contact with the handle full time, but everytime I assume something that's so easily preventable I end up learning something new at the worst possible time.