rykoala,
'Good on ya' for doing what you can to optimize mpg when driving this beast. If you use as many as possible of the tips here you'll certainly do better than without them.
I formerly drove a Volvo 240 wagon, EPA 17/22, and in good summer weather got 30-32 mpg out of it on a 1-hour, 60-mile highway commute. I didn't do any weight reduction in terms of parts removal but I did some other mods and changed my driving habits, similarly to what you've been doing. Notes on my mods to that car are here:
Sven - Volvo 240 wagon
I'm not saying you should do the same mods I did. But I do think that combining whatever mods and driving techniques you can, will give you good gains.
Good luck on it!
And may a far more FE vehicle, suitable to your needs, drop into your lap at little or no financial cost to you! Be sure to grab it when it appears.
BP