“My confusion is in regards to the similar meanings given for both sankhara and dhamma. If I remember correctly, some of the descriptions like “without substance, no safety, meatless bones” for all sankhara, were also given for all dhamma. ”
Hopefully, the confusion can be resolved with the following example.
Apple trees are also trees. But only an apple tree can produce apples. Just because apple trees belong to the category of trees, any other tree cannot produce apples.
In the same way, sankhara are part of dhamma. But just because sankhara are of anicca nature (cannot be maintained to one’s satisfaction, like a meat-less bone, etc), other dhammas do not have such anicca nature. But sankhara also have anatta nature (without essence), because they are also included in Dhammas.
In set theory, apple trees are a “subset” or “a part of” of the set of trees. The set of trees is the bigger set. The set of apple trees is a smaller set that is within the larger set of trees. Only apple trees can produce apples. But apple trees also have other characteristics of trees: roots, trunk, leaves, etc.
Does that help?