Don’t be so hard on yourself. A dumb ass is someone who doesn’t even know that they are ignorant. You are at least aware that you’re new to the game.
But in any case, to move onto Craig’s objection. Those properties of a horse are in reference to his parts and only inform insofar as the horse is composite, whereas goodness, power and other attributes of God is in reference to characters (which are holistic). While a horse has characteristics that pertain to the whole (like being mammalian) having a butt is only true insofar as the horse has that part of its anatomy. So, it would seem that this analogy ignores the character\property distiction and attacks another conception of divine simplicity (I think Thomistic and not Anselmian).