1) Rockbox gets similar battery life to the original firmware now. As well, it is not actually harmful to charge your battery every night, and in fact long, full charges are more harmful to the battery.
2) Rebooting will drain some battery, but watching video drains so much more as to make the amount insignificant.
3) We do not provide support for the iPodLinux bootloader, and while it may work to boot Rockbox now, there is no guarantee of continued functionality in the future. We only test against our own bootloader, and update it as necessary.