UPDATE: I've fixed the .CDI image!
I did a clean rebuild, then made a .ISO with MKISOFS and then just "BIN2BOOT vmucd.iso /nohack". I burned the disc, tried it on my Dreamcast and worked perfectly. yeah!
Again, sorry for any inconvenience and wasted CDs

Please post if everything works fine or not, I don't want to screw many DC fans again.