Those graphs look pretty clean, a might too clean I would say. Not that I have a 1950s RS56 laying around, but I’m going to guess it was a bit more noisy and added a bit more distortion than this plugin. So — if you were dead set on perfectly re-creating the character of this vintage tool which was first used in mastering for vinyl cutting, you will be disappointed. You know, since you are obviously so familiar with that sound and all.
Pair this up with the Waves REDD .17 or .37 and you will simulate how it was first used at Abbey Road. They used the preamps on those boards to bring the (passive) signal back up. Those emulated preamps in the REDD plugins have more than enough THD to make up for the “quietness” of the RS56, and you can use it as your channel strip EQ instead of the “built-in” one on the REDD plugin. Only use four channels and pretend you are George Martin!