Well, the cassette body is steel, I verified with a magnet.

The threads were also undamaged. When I tore off the lockring with a giant 18 inch wrench, I looked at the threads on both the lockring and the cassette body. Looked surprisingly good for something that was cross-threaded. A little bit of dirt, I wiped that away and applied some marine grease and tried tightening on the lockring using my fingers first only before I busted out the wrench.

Of course, the wobble in the whole cassette was still there - symptomatic of something not right.

For a while I actually thought the smallest cog was BENT. I had, after all, put it in the dishwasher and dried it in there too. I couldn't help but wonder if the high heat might have slightly warped the cog. It wasn't LEVEL on the rest of the cogs.

I quickly dispelled that thought when I took off the cog and put it on a level surface and found that it lined up perfectly on the surface.

I then realized my mistake - I didn't properly align the teeth of the sprockets on the cassette body!! Wow! What a dumb mistake!

I aligned all the teeth this time and tightened down the lockring using finger pressure only and what do you know! No more cassette wobble! I then pulled out the wrench to get to 40 N*m or whereabouts!