Okay, if you're having trouble with kaupenjoe's tutorials it's because he assumes you already have a solid understanding of Java, so he skips over explaining that aspect of what he's doing - which is a lot, since it's all in Java. This website should be very helpful in understanding whatever methods or parts he uses in his videos.
That's where they are now, inside resources/assets/mod_id/ (unless I did not understand soomething in which case sorry)
I tried changing the name from plural to singular (textures->texture, blocks->block) but still does not recognize the textures
EDIT: Okay that was the error. I have come back to my mod after a month and I forgot I had to change the texture json file from plural to singular too, so you're right
There's a mod version mismatch here.
Fastbench wants a more recent version of Forge than you have.
I suggest checking if there's a new version of the All The Mods 8 server package, or if not, asking the All The Mods Team, since this seems like a large flaw.