Thanks for your response, but you missed my mention of using a Nitty Gritty Record Cleaning Machine, which is a vacuum cleaning machine.
I have used very similar practices to yours--LAST preservative, then routine cleaning with a carbon-fiber brush after using a Zerostat gun. I also use the LAST stylus brushes, Onzow Zerodust stylus cleaner and LAST stylus preservative, and my stylus has over 1000 hrs. on it and still sounds fine.
For deep cleaning I've used the LAST "First" cleaner, Nitty Gritty fluid, Disk Doctor and others, and I'm afraid these particular records may be like your hopeless 1%. It's a shame because they are otherwise largely free of "ticks," "pops," and what-have-you.
I'm wondering if something different like the MoFi "enzyme" cleaning fluid or Dawn dishwashing detergent (well-known for cutting grease, removing fingerprints, etc.) would give any different result than the cleaners I've used.