Objective reality and free will you are missing my point and the point of the original post.
1. The very notion of "objective" is rooted in substance ontology, i.e., the subject/object distinction.
2. The subject/object distinction is the Cartesian distinction between two self-sufficient substances, i.e., thinking substances (having non physical attributes) and extended substances (having physical attributes).
3. Being self-sufficient, thinking substances (minds) are completely independent of extended substances (physical things). Similarly and being self-sufficient, extended substances (physical things) are completely independent of thinking substances (minds). After all, self-sufficient does mean self-sufficient.
Therefore, when you claim that there are only physical things, you are rejecting substance ontology.
And that is okay. But you need to recognize that you are doing that.
Otherwise, you end up trying to resolve a problem from within a paradigm you have rejected.
Welcome to contemporary man's Cartesian nightmare.