I've looked it up and you could try using Rinput to try and get raw input from the mouse. Not sure if t hat would do anything. https://pcgamingwiki.com/wiki/Max_Payne_3#Negative_mouse_acceleration_and_frame_dependent_mouse_sensitivity
Although you can't get around the lack of a sensitivity number, this page I found on Reddit tells how you can get rid of mouse smoothing and acceleration.