Thanks for the responses, they've been helpful.
To update my learnings and current situation:
1. Tank removal and cleaning option is more costly than I thought. After further investigation it involves about 4 hours to remove tank ($95/hr), sending tank to separate shop for cleaning ($300) and 4 hour reinstall, plus loss of fuel, so about $1500.
2. Found one fuel polisher in the Raleigh, NC, i.e. my local area. They looked at RV and found no good way to circulate and filter system due to physical set up.
3. Same company recommended shocking tank with a biocide to kill suspected biological growth and dispersant to "dissolve" resulting deposits and sludge. However, they first recommended analysis of fuel for bacterial growth (30 hours wait) and fungus (72 hours wait). Both tests were negative, suggesting sludge on my filter was not "algae", but fuel decomposition products (asphaltenes).
4. Bought some additives (Power Service Diesel Clear) to clean up tank by dispersing deposits. Have added this and will now embark on 3,000 mile trip next week, sure hope it works. Just in case, I will also carry 2 spare primary fuel filters.
5. On trip will meet up with friend from Baton Rouge, LA. He left home 2 days ago, with an 8 year old diesel MH that never had a fuel problem. Before he reached Dallas, TX he experienced severe power loss. Took the unit to a shop in Sherman, TX and computer checks showed the problem was a fuel restriction. A filter change solved the problem, at least temporarily. He went on to Santa Fe without further problems. Of note, the shop in Sherman said they have seen numerous RV's this spring with fouled fuel filters, which they attribute (based on speculation only I'm sure) to RV's sitting over the winter with ULSD fuel in them that apparently is less stable and forms decomposition products more readily than LSD used to do. I don't know if this is fact, but it's interesting that my buddy saw no problems for 8 years and now has a fouled filter, and I have a 3 year old unit that also had a fouled filter, both RV's being on an ULSD diet since 2007.
We'll travel together to the Rockies over the next month and compare experiences. On my return I'll update this note. I also plan to use a fuel stabilizer between trips to try to prevent further problems.
Any comment from others having experienced similar problems will be appreciated.
Thanks,
Larry