Welcome to the site atfab.
I'd start with a look at the
65+ mods list we have. It is a good list of proven modifications. While you are at it, I would definitely take a look at the
100+ hypermiling tips which will help you change your driving habits. It seems you are doing pretty good, but driving techniques have huge impacts on mileage, so its worth looking into.
As for a 100 mile EV, its possible, but pushing it. To go that far, you really need a lithium ion pack which means a fair amount of money as lithium is currently 2.5X the price per Wh vs lead acid. I don't want to discourage you, just letting you know.
