That is certainly unfortunate. I remember you posting your mix room about two weeks ago on here. Hard room to treat. I would have much rather kept the space one large area and just use gobos or a large curtain to separate yourself while tracking. Usually in a small space, converting it into two rooms can pose many more problems than being helpful. On top of that, the fact that your control room is such an odd shape with a strong angle, and objects on the other wall, I wouldn't expect it to sound very accurate in there. Though treatment can help,
I think (unfortunately) it may be more worth your time and money to rip down the wall and go for a reflection free zone around your mix position while treating the rest of the room sparingly for the recordings. This is just my opinion though, I would weigh in other advice aswell to see what is more do-able and practical at the moment. For example, if you need to build treatment in either set up - do it first and try it out in the rooms. If you can get good results, than stick with it..if not, tear down the walls and use the treatment in there
Good luck, keep us posted!