Bentham saw pain and pleasure not only as objective, but as fungible forces with no meaning aside from a numerical value; he treated them like one would treat the wind or temperature. J.S. Mill added the personal component of pain and pleasure as personal experiences with subjective value.

Frankfurt School critical theory, in particualr Adorno, has elevated the idea of suffering to a central consideration of philosophy. You may find some good material in their writings that connects with your ideas expressed here.