You were on the right track with the 5sp!!! The 5sp transforms it. More power and econo, if you can believe that. Maybe the wife could be persuaded to learn? If she has anywhere near normal levels of hand/eye coordination and a strong enough clutch leg, she can do it.
Failing that, I've found that my a/t Tempo likes 185/75R14s- one size taller than stock. Perhaps even taller than that would be better yet but I haven't tried it.
You can adjust the TV linkage for earlier upshifts.
Air the tires up to at least 35, if not 40. One can go higher yet, but I haven't seen benefit to that.
There ain't a whole lotta weight to strip out unless you get serious and gut it all. I don't see the wife going along with that. I just make sure I don't have extra junk in the car. I tried it for a while with no pass. seat, no spare and tools, etc., but eh, I don't have much city component to my driving so it didn't really help.
As you can see my a/t Tempo is just under 28mpg. It can do 30 or a bit better on a good day. If you visited my gaslog you will also see it hasn't been updated for a long, long time. It's parked and I run my 5sp. If you are getting 28-30, I think you are pretty much doing it right. If you get more... tell me how!!!
Speed kills econo especially on the a/t Tempo. No OD ratio, it's like trying to cruise the 5sp in 4th gear. Seems like you can watch the fuel gauge drop at speeds above 60.