Hi,
Ok answer at your questions:
My pc is able to boot on USB because I got a live linux and I'm able to boot on it
Maybe the make_bootable script don't ran correctly but no message indicate it
ldlinux.sys, ldlinux.c32 and the folder syslinux and I got the folder syslinux and files in it
Very weird problem! I'm a sysadmin for many years I don't understand this one.