8.5 shot is very small, don't see how it would hurt the gun. The only issue I might consider, is if tungsten is much harder than lead. There are special choke tubes for steel shot to keep them from being damaged from the hard steel. If tungsten is hard like steel, a steel shot choke may be in order??
But then again, if they sell it for the 28 gauge, surely it is safe in it. You can always call the gun manufacturer to verify and or maybe the ammo manufacturer.
I have seen the #9tss for .410. I didn't read on the box to see if there were any warnings.
Hopefully so BUT in my experience it is not safe to assume anything about the shells made and marketed by Hevi as they change stuff around a bunch as they go.
I would buy from someone like Apex or Foxtrot ammo and feel real good about the load quality. They probably both use the same recipes and components that I do.