I dont think you have to logout in an inn to get rested bonus. As long as you see the moon symbol at the end of your exp bar, you should be in a good spot to log.

I dont know any of the specifics but im usually on one of my lvl 50s and i can see the rest bar overlapping my exp bar. Once it fills up most of the way, i play one of my lower lvls for awhile. You will see the bonus display next to the exp given upon kills in your chat text. This display is combined with other bonus types though... fc, food, chain kills and such.