How does the cosmological argument commit a special pleading falllacy?
How are you not commiting a straw man fallacy when you make God something other than The Ultimate Reality?
A fallacy is a "a false or mistaken idea".
Created things have beginnings and ends. The Uncreated doesn't. God is a persistent existence.
The fact that you claim to believe in true things while at the same time denying God in itself is a fallacy because if there is no Ultimate Reality, nothing is ultimately true.
You can go around pointing the finger and going "logical fallacy" all you want, but as long as you are denying God, you have adopted an indefensible and foolish position that if taken seriously undermines everything you say.
You, after all, don't believe in The Truth.