Stop the presses. Stop the presses now. O.k I am glad you are taking responsibilty for what you did wrong in the relationship, but there are some big things that stick out for me. You had a vasectomy before your 2nd marriage, and your now wife knew this. Wake up alarm!!! She married you knowing this and she knew it would take surgery to get it reversed, and she decided not to even talk to you about it before saying "I do". We all know now that these things like kids, parents, house, need to be discussed before marriage so I'm not faulting you or her for not, but she should have been accepting of the consequences of not talking about it resulting in the delay.
Second of all your step mother seems like a witch with an attitude. Not to get too biblical, but God tested Abraham with his son Isaac on Mount Moriah. He asked Ab to kill his son on that mountain and Abraham was prepared to do this. Metaphorically the Bible was telling us that parents need to "let go" of their kids when they turn adults over to God. They need to release the reigns over to God and just love their kids. Now your wife, an adult, has entered into another contract with God called marriage. Your stepmother is refusing to "let go" of her daughter over to God and respecting her daughter's marriage. I honesty think this woman is damning your marriage and slowly destroying it with negativity. It was or is your wife's respsonsibility to step up and tell her mother to butt out.
Marriage and other relationships is about two people. It is not entirely your wife's fault, but it surely is not all your fault. Don't put all the burden on yourself. You don't need to tell your wife this, but don't feel completely guilty.