I think you are going to have problems when you angle the blade. Snow is very heavy and has great mass when plowed. With the moment arm of the blade way out in front of the tractor CG, and the lifting force encountered when pushing the loader into something in float, I think the front end is going to go the opposite direction that the plow is angled, with any appreciable snow build up in front of the plow. I helped build a plywood plow for the front of a 250CC quad, and this was the problem when we tried to angle the blade. the front would just slide off the other direction even with full steering . Someone setting out in front of the handlebars improved things a bit, but there just wasn't enough lateral traction to maintain a straight line against the side force of the snow on the angled blade.
In your case, more weight in the back will make the situation worse as it will effectively shift the CG toward the rear and lessen the weight on the front axle and the laterial traction it provides.
Loader arms are also not particularly strong in the side axis, and again with the point where the force will be applied being way out in front(long moment arm) the potential for loader damage might be pretty high. I can't tell you how many solid objects I have hit under the snow, and this is quite common.
In my snow plowing experience, the speed at which you plow can really enhance plow effectiveness by storing a little energy in the moving snow as it curls up the blade. But with the blade way out on the arms, I would think too much speed, enough to get this type snow movement, would be a bad idea. It is afterall a front end LOADER, not a PLOW...
At a place I once worked back in upstate NY, we had a JD 4X4 tractor with FEL, about 40HP, I forget the model. It had a full cab and was a pretty nice machine. We fabricated a custom mount for an old pickup plow we had lying around, similar to the one you have used. Our mount however was attached to the front of the frame and again back behind the front axle, similar to how some of the truck mounts are attached to the frame. We had a single hydraulic cylinder to lift the front of the plow frame, and with the plow straight, we could just lower the FEL bucket down in front of the snowplow. You did have to have the bucket raised to angle the snowplow blade, and you coundn't get the original manufacturers angle on the plow with it so close to the front as it would contact the tires, but it worked great! A bucket full of snow kept the front end loaded as good as, if not better than the pickup plows I have used. We got a lot of snow in Upstate NY, and when the banks built up, you could push the snow as far up against the bank as it would go with the plow, then back up a little bit, and use the loader bucket to lift and push the snow up and over the top of the bank. No changing cold steel parts to get a different impliment on, everythig you needed was already there ready to use. The plow mounted/unmounted just like it did on a truck, with 3 pins and 2QC hydraulic fittings.
If I had enough snow to warrant a plow, I would probably configure a mount that conected to the rear drawbar/axle, and use the 3PH to raise/lower the blade. But that is just me, and I have always been a little bassackwards
