The article seems to assume a big cock in a small (pony) mare vagina.
My experience with an average man cock and a full-sized mare is that she will hardly feel you penetrating. For pleasuring her, I use my arm, and I stimulate her clitoris with either finger or mouth.
Thank you for sharing. I'm so sorry that you attempted to end your life. Guilt is a choice. You don't have to feel guilty, nor should you. You're harming neither yourself or anyone else so long as the sex between you and your non-human partners is consensual.