https://www.mediafire.com/folder/uoh63n6d3g7nf/unarmed+bug < - save file of example with enemy nearby for testing, taking the Improved Unarmed Combat feat does not seem to boost dirty kick despite dirty kick being based on unarmed damage.
Additional minor bug: Taking improved unarmed combat does not change the unarmed damage in the character damage menu when wielding fists (the one that appears when you click C) however it does boost the damage in practice.