Tried to add maximum damage per your suggestion to delete min dmg, and while the tooltip is accurate, it is not registering the dmg in game. I was able to work around this by modifying an in game found max dmg jewel, when I edit it, it shows adds max "integer" twice and a mod called item_throw_maxdamage "integer" that I can't find in the list, but is present on an in game found item.
max damage is indeed a complicated attribute, and it doesn't work on all items. Have to look into this in more detail when i have time