Your 27% FE improvement is a major achievement.
Don't forget to pump up your tires. Up to the max pressure
as shown on the tire sidewall should not be a safety issue.
Also, FE in colder months is reduced due "winter gas" with
ethanol.
You're on the right track, reprogramming how you drive has
the greatest potential for long term FE improvements. It takes
considerable time and effort to incorporate/internalize the many
little tricks and use them effectively in the dynamics of everyday
driving. I think that you've reached a FE plateau from picking
the "low hanging fruit."
Keep up the good work