I couldn't find something to show battery state and there is no screensaver or something to turn the display off after some time but putting the cover on turns the display off and it doesn't consume much power (well if there is wifi or bt running it'll turn off soon enough just because putting the cover doesn't turn them off automatically) but I suppose its just in the same standby mode as the official image. And if someone has the time to fiddle some screen saver should be easily found.
I think installing dual boot menu and using a card reader is the easy way that should do. About the size its something like a 350mb left from 1GB card.
About the onscreen keyboard I think its the fastest way for input but cellwriter should work after compiling it just because I have a feeling I woun't find it in the repos