I'll have a look, but I think the latter part will mean database changes, making it incompatible with the upstream version, which I'd rather not do. You could use the tags to flag read books though, and there's some code done for filtering (though it doesn't look to have been completed yet) which I may be able to do something with. That should allow you to check & filter read books.

Well, the option is "Always use my font" which I think just overrides the font-family. I'll have a look though - it ought to be possible to override the font size as well.

There's no reason these couldn't go on the toolbar, but that'll have to wait until I've finished writing the menu/toolbar customisation app. In the meantine, you can use the volume buttons to change pages, or enable the "single tap" option for dictionary search (though you then need to be careful of where your swipe starts, as I think the search is triggered on press rather than on release).