Two points of install where disk identification fails

Question

I've been installing Arch every three months or so for the last year, on different machines, and each time, there's the same two failures. I thought I'd document them here and hope for advise on how to get around them, and/or some way to fix these failures in the install scripts.
I download ISOs and put on a large, FAT32 formatted USB stick, that also has the UEFI boot loader. This gets me to the main boot menu (boot i686, boot x86_64, run memtest, etc.)
When I then select to boot i686 or x86_64, I end up at the "waiting 30 seconds for ARCH_201212 to appear," but that label never appears.
(*1) How do I pass sufficient information from the main boot menu to this boot section so it knows how to identify the ISO device it's booting into?
At the command prompt, I can mount /dev/sdb1 (the FAT file system containing the ISO) on /mnt (after creating /mnt) and then mount the ISO using "mount -o loop" on /run/archlinux/bootmnt (I'm typing from memory -- I think this is the place.)
However, the label doesn't always appear here, and the script *only* looks for the label, not for the mount already being present.
(*2) How can I change the boot script that runs at this point to look for some sentinel file at the target mount location, rather than just wait for the label?
Once booting, I can move on to install various packages, chroot, genfstab, and all that good stuff. The Grub installation is somewhat poorly documented on the Arch Installation wiki, because the first part says "see system configuration" and the system configuration says "see first part" without actually discussing grub-install or anything...
However, when I come to the point of re-booting after installing grub, the boot fails. The reason for the boot failure is that grub is looking for a disk by UUID. The disk UUID it's looking for is not the actual disk UUID of my system partition (or any partition in my system.)
I don't know where the UUID it's using is coming from -- is it there from one of the maintainers? Is it the UUID of the ISO disk? Something else?
(*3) What do I need to change in my grub installation to make it actually look for the right boot device?
Finally: When I tell it to ignore the Linux UUID, grub-install fails, saying it can't get to the appropriate device at boot time. This was using grub-bios; I haven't tried grub-efi on this particular machine. I have my /boot ext3 partition on /dev/sda1, my / nilfs2 root partition on /dev/sda2, and my small swap partition on /dev/sda3.
Also, if I wanted to make changes to the install/boot scripts used by the bootable ISO, so they worked in this situation, what do I need to do to:
a) find the boot scripts used?
b) create a proper ISO?
Is there some set of packages and scripts I can install to create the bootable ISO medium simply, to get a reasonable turn-around time when testing?
Is there any documentation of how the boot scripts in this environment fit together, where they live, what their configurations are, etc?

Answer 1

jwatte wrote:Thank You for your answer.
That page doesn't seem to talk at all about why grub installs looking for the wrong disk when rebooting.
It also doesn't talk about how these scripts start up or where I can find out about developing in them.
Given that I use memdisk on windows, I assumed the other sections aren't applicable .
I'll see if I find anything in the other sections and update the wiki if needed for clarity on part one of three.
I meant that it answers the question about labelling the usb installation media. (Either by labelling it or setting it up differently.)
The grub wiki page would be the place to look for information on grub. There have also been a lot of threads about the cannot-find-root on rebooting following grub installation.