Your fstab looks a bit weird - there are many lines that are commented out and will not be read:
#/dev/sda1 /boot ext3 defaults 1 2
#/dev/sda2 /usr ext3 defaults 1 2
#/dev/sda3 /home ext3 defaults 1 2
#/dev/sda5 /var ext3 defaults 1 2
This means that these partitions will not be mounted automatically. So if you have booted with this configuration you will have your home directories in /home on the root partition instead of on /dev/sda3. When you mount /dev/sda3 to /home, your files residing in that directory (the /home on the root partition) will become inaccessible since you have used that dir as a mountpoint. They will still be there on the root partition but /home displays the /dev/sda3 file system.
I hope that made some sense, but I'm not sure it did.
You could create a temporary mountpoint for /dev/sda3 - say /mnt/tmp_home - and mount it there, copy over the files (as in your second post) from your old /home (on the root partition), and when you're done, unmount /dev/sda3 and mount it as described in your fstab. Uncomment the /dev/sda3 line in fstab and next time you boot your homes should reside on /dev/sda3.
The same applies to all the other disabled lines in /etc/fstab, I just used your /dev/sda3 (/home) partition as an example.