I did basically the same steps in my persistent USB thumb drive, as described in the BT Wiki (your last link). But instead of using syslinux on a fat32 partition I would do it the direct and simplier...

Hi,
my aim was to make a multi boot USB thumb drive with 3 primary partitions (all formatted with ext3). The first one is the boot partition, got a size of 4 GB and was created for BT5. This...