Sakeeeee

Really glad you've made it ! 
 
I looked at your files locations screenshot and there were in deed some things I wouldn't do the same. 
I got 833 vehicle files in my custom cars dlcpack's vehicles.rpf (.yft and .ytd), so you can bet I've already encounted my part of problems with some models I've downloaded, so I've learnt that the more simple you do, the better !
 
I don't know the Albo's configuration (although I'm sure it's for the best, as I know his professionalism), but as you told me to do so, here's my advice for another dlcpack you would add in the future :
1. Create your "dlcpackname" in mods/update/x64/dlcpacks
2. Add the lines needed in mods/update/update.rpf/common/data/extratitleupdatedata and dlclist.xml
3. In your "dlcpackname".rpf, here's what you need to find
 
 
4. In your data folder, here's what you can have
 
5. In your x64 folder, here's what you can have :
 
And everything works just fine ! Multiply the folders raise the conflicts risks or the issues you can encounter by using modded car models...
 
Anyway, good news your problem is solved ! Have fun :)