If you are experiencing a lot of swinging with your rear blade, I wonder whether there might be excessive slack in the turnbuckles on the lower arms of your three point hitch. Just a thought.
I use a rear mounted snowblower. My driving skills are somewhat suspect I guess. If I go too fast I still wander side to side like a drunken sailor.
Full bucket, I keep the turn buckels fairly tight. The swing of the rear blade I'm talking about is just the physics of the way the tractor pivots on the rear axle when you make turn.