lol, this isn't a new unit, it's just a recolor

Added 17 minutes ago

........ that is, you have some kind of unit pack, to remove a creature from the game, you just need to remove it from the MapObjects\_(AdvMapSharedGroup)\Monsters generation list - this is where the random generation files are located

after that, the unit will stop appearing in the game; in principle, this is the same as deleting the unit (this is an option for the lazy)

2) everything is simple with dwellings
at the very bottom of any dwelling, the ID of the recruited unit is written, for example, a peasant hut:

.........................

   
        CREATURE_PEASANT
   
    DWELLING_TYPE_SPECIFIC

replace PEASANT with the unit number, and that's it

3) I don't know about the damage

Added 7 minutes ago
the problem with the griffins from BDT is that it's a texture-recolor; you can extract the griffin from RTF - it's made according to the Zahar template, so you can easily make it a new unit, and then add the textures from BDT on top