You're doing mostly highway? My
build thread for my previous car should be of some interest. I averaged just under 50mpg over two years in an EX with manual tranmission. You'll find pictures of my mirror delete and front bumper project in there too. I had custom coilovers as well, but those were from when I autocrossed the car; now I would find cheap lowering springs (like I did with my current car).
If you don't mind your trunk looking raggedy, you can ditch all the trim pieces and floor, but leave the spare. I also removed the front speakers, sway bar, possibly some other things (it was a while ago).
I replaced my stock alloys with heavier steel wheels with moon caps--I think improved aerodynamics trumps weight any day, especially when we're talking small differences like wheel weight. Insight wheels would be the best of both, but I don't know if they fit. Considering you already have the steel wheels, I would put smooth wheel covers on (you could make your own out of coroplast or pizza pans, even) and call it done.