As I reply to this, I sit here with my step daughter who is now 26 years old.....and hated my very existence the first 8 years. Her mother and I were never actually married but now she comes to me for advise or guidance. It's not easy to be a step parent and you will ALWAYS be wrong in someone's eyes. But once they grow up they will love and respect you for always caring about them first! I have had 5 step children out of two different relationships. I do not have all of the right answers but if you ever need to talk about it I'll help if I can. You said your wife is behind you 110%. On discipline.....She really needs to be out in front of you 150%, and if she is not as stern with them when you are not around as when you are they will always see you as the bad guy!!!! Being a step parent is the biggest challenge you will ever face....and it can be very rewarding also. My stepson's friends are always surprised to find out I'm his step father because he tells them that I'm his dad.