OK, if you have read this far and are still open to suggestion here goes:
Clean the threads with solvent, use a good permanent thread locker compound, a bb lock ring, and rotafix the cog on.
I had five bikes set up this way, rode them for years through all kinds of weather (CLE, OH) and up and down many hills without a rear brake (except on my winter commuter) and I never had an issue with the cog coming loose.
I am ~200lb, I skid, and if you read my shiner post you will see that I just locked up the back wheel and the cog did not spin off.

Is it the best idea? no Can it be done with lasting results? sure

Enjoy