I'm a little late getting into this conversation but have you thought about this?
Ospho OSPHOG; Ospho Metal Treatment Gallon Made by Ospho
I've had good luck removing rust with it.
Blades have to be constantly adjusted, they are not a set it and forget it piece of equipment. I went with the pin type rhino and sure glad I did. I'm considering adding hydraulics now because of the constant adjustments needed when building roads. By what you need and don't settle for less is...
For a rear blade to be efficient it needs to be heavy and adjustable. If you have that you can do a good job from pulling ditches to crowning a road. So with that you need a strong tractor. If you don't have either and have a smaller tractor I would suggest a pull box blade to pull dirt and level.
I think I remember old guys saying they used hickory down her in the south. I'm pretty sure it was a very dense wood. If you can post a picture of the disc set, I haven't seen one like that in years.
For utility work the MX is great but for farming activities I'd move up to the M. I love the HST for grading, grappling and bucket work. I went the biggest most powerful they had with the HST. I don't farm but rather bush hog and plow fire lines, remove trees and maintain 1/2 mile of roadway...
Are you keeping your rpms up? If so there might be a problem with the pump. I do believe the bucket is larger on the MX but still it should lift a full load of dirt. How does the weight of the rocks you're lifting compare to the weight of dirt?
I built this in haste a year ago, it's simple but actually works. It's never fell or was knocked off so I guess it works out. Thought about upgrading it but haven't made the time