Not quite clear what you are trying to achieve. There's negative feedback implemented for the common mode circuit but not for the differential mode driver path itself.
It's unusual to specify the differential driver behavior by an open loop gain, but you can expect maximum gain at the differential output zero crossing. The input stage of the LVDS driver isn't shown in the schematic, respectively we don't know what the real measurement setup is. Common mode output should be simply set by the existing CM control loop. CM input - if applicable. What's the input stage interface standard?