Re mounting the .iso.
Specifying the fstype (-t iso9660) is _usually_ unnecessary. Mount almost always autodetects fstype. Also, specifying the actual loop dev (/dev/loop0) could cause problems if that device is already in use. If you simply do:
mount my_isofile.iso /path/to/mountpoint -o loop
then the first _available_ loop device (loop0-loop7) is allocated.
As to No. 4, that depends on the boot method (ie., grub, el torrito floppy emu, isolinux, etc.) being used by the original .iso image. I like isolinux myself. The short answer is that mkisofs has options that can make the resulting cd bootable. You might want to grab the isolinux tarball (or at least the docs) and also RIP (Rescue Is Possible) docs. They have some good examples. Iirc there are some ldp Howto's. And of course man mkisofs.