Firstly hello, I've skimmed this thread and welcome of recognising the savings you can make with the right car. You seem to be well on the right track but I wondered about a couple of things.
Firstly tyre pressures - have you experimented with going higher ? My factory setting is mid-30s but I run 40+ most of the time. When I got my car in July last year this was the mod that made the instant "detectable" change. You may need to go high and then back off for ride comfort but you shouldn't see a drop in grip - it may even improve.
Secondly an instant MPG readout of some kind is worth the money and will pay you back. We didn't get the "Mazda Escort" here in the UK (we got an altogether worse car...) so I'm not sure if a Scangauge or similar will work. If not there are other options but any kind of readout will pay you back over time.
But based on your history so far it seems 40+ will be yours quite soon.
And as you tap the savings can be put into other stuff like fun cars, trips and so on.
