I can understand why a man of 58, who has already raised three children to adulthood (he's probably a grandfather too?), would want to have the responsibility of raising another baby at this stage of the game.
And he is still married, and does not wish anyone to know he has fathered a child. He has made it clear that he won't be in your life, or take part in raising this baby. I assume you will have to settle for him tossing cash your way to help out. (you might want to establish child support legally)
You will have your hands full with having already a 14 year old, and now a baby. Single motherhood is quite different than shared custody, which the father doesn't appear to want either.
So what are you left with.
It is possible that at some point, he may, out of curiosity, wish to see, or be a part of his child's life, but to sit around and wait for something that may never happen, you are robbing yourself of the freedom you need to move on. If it were me, I would presume the relationship is over.
That he is on dating sites, tells me that he's interested in a relationship with a woman, for purposes other than marriage and children. Relationships come in all shapes and sizes, but, I presume from what you have said about him, he is not interested in a relationship in order to start a family.
My advice to you is to be prepared to raise this child, with financial support from him, and nothing more.