Well, I would say either you are doing to much with the wrong things, or the track is such that it's just not going to get to this level. -9 or -8 rms is not really saying anything about how loud the master is. just how much it's moving a meter. If it's a very dense mix that doesn't let up, you may never get there nor would you want to listen to it if you did. Plus i've never been able to get good quality high level output from plugins that i can from high end outboard. So I would abandon the level goal and just make it sound good and reasonably loud. I personally wouldn't use 2 limiters. If you treat the mix properly before the limiter, one should be enough. And why are you compensating for dither? If your dither is making that much of a difference that you don't want, then choose a different less damaging one. In general, my guess is you are working too hard on the mix. I would zero everything out and start over, simpler, less plugs. get it to sound good. If your level is not there then really sit and listen to why it's not there. maybe you are smashing the low end too much. More low end = more rms.