(1) - Assuming for a sec your lv is mounted on /home:
# umount /home
# resize2fs /dev/myvg/homevol 524288
# lvreduce -L-1G /dev/myvg/homevol
# mount /home
_should_ do the trick.
(2) I'm not sure... pvdisplay or pvdata?
(3) If pvmove isn't an option, I would say the answer is "no"
(4) Depends on what is on the disk (and in the volume group). If /usr, or /var is on there, I suspect your system won't boot very well
Excellent LVM HOWTO: http://www.tldp.org/HOWTO/LVM-HOWTO/index.html
Hope you can find some more info there to help you further along.