Vincent was also the one that rebuilt the Order after it sort of went on hiatus after Dahlia's death back in 1980 or '83 *depends on which timeline you use*
There's a part in SH3 where Vincent says "I built this church with my power! The power of money which you view with such scorn!" It can be surmised that Vincent used his money to rehaul the Order.
As for Vincent's deal with God, he says that he fears and adores her, but he doesn't want her born because it'd be too unpredictable. He also mentions loving the pleasures of this world. I think Vincent knew if God were born, then his "paradise" would be gone.