As with any tractor, to do the maximum lift you'll want lots of ballast weight hanging on the three point (lifted only high enough to clear the ground as you move about).
You might do well to drop the SSQA bucket since the loader is rated with weight of the standard bucket in place. The bucket weighs a few hundred pounds, dropping the bucket and chaining to the loader itself might give you what additional capacity is needed.
I honestly think they underrated the lift on the ML120 loader from my experience with my own. Just so long as you have enough weight on the rear to hold the rear down, I think you'll be ok. Worst case it will grunt and say "go call the neighbor", nothing will break unless faulty.
Most things I couldn't lift, I've lifted the rearend trying (which has loaded tires and up to 1500# on the three point).
Also keep in mind maximum lift will be at the rated engine speed for full hydraulic flow, you'll not do the lift at idle...