The deal with the FS program that makes it better for in-town driving is the stock-ish low boost fueling and the early upshifts. For all intents and purposes, there are relatively few fueling and injection timing differences between it and a daily driver or performance tune at a cruise speed/load condition. You should not notice much of a difference in economy between an 80HP DD tune or Fuel Sipper if you're cruising down the highway all the time.
I think that covers the first two questions.
Lastly, I think that the originally-offered Fuel Sipper was an 80-ish HP program and the 65 HP came out later.
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Tuning, PCM flashing, and burning chips for 7.3s since 2008. Repairing all aspects of 7.3L Powerstrokes for 25 years.
Eight 7.3L PSDs in the driveway including a 1994 Crown Vic and 1973 F100/2002 F350. Looking for the next victim.
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