You can call the following function to get the level of a given crafting category:
$gameParty.getCraftLevel(category)
The above function pulls the info from an object in $gameParty that stores all category levels; $gameParty._craftLevels. You can also call that object directly and append a category name to the end of it to get the level without using the function. $gameParty._craftLevels.blacksmithing for example.
You can also use the following to get the current experience value of a given category:
$gameParty.getCraftExperience(category)