powersaving is a setting in battery settinig on officila rom. it can save battery in when phone is sleep. http://www.careace.net/wp-content/uploads/2011/09/power-saving-mode-e1316830124123.png
O. When you hit 30%, it disables Haptic Feedback Wifi data? I think High brightness Kills lots of running apps Essentially puts your phone in a low state mode, so that you can call / SMS, and thats about it. I put mine towards 10%, because I require all those features until I'm really really low on battery.
I don't know. You may wish to make a topic in the Defy forum and await an answer there. http://miuiandroid.com/community/forums/motorola-defy.48/