I have been reading several varied posts here and gotten quite a bit of useful advice and information, but if anyone can help me with specifics on my own dillemma I would be very grateful. 

I'm a 29 year old male working rotating weekly shifts at a 24 hour factory. My girlfriend is a mother 24 year old mother to a 4 year old daughter (ZB4). She is also a preschool teacher with a 30 minute commute. This means that during certain weeks, my SO and I spend next to no time together. And over the last few months, ZB4 has evolved from a peaceful toddler to a terror - at least for me. 

Before I go any farther, I need to explain a bit i feel. I've had a vasectomy to avoid ever having children of my own, but I could not help myself with this woman and she has even prevented me from leaving her. We both want this to work but i don't know how. 

ZB4 has never had any real discipline. She will crawl in between us when we are cuddling or kissing. She is unable to be alone for more than 2 minutes at a time. If the TV isn't on one of her shows we hear about it till it's changed. She screams about being hungry but refuses to eat when the time comes. She destroys things and bangs for attention when left to herself. She is even unable to out on a coat by herself and will scream and throw a fit till my SO puts it on for her. I should stop here. So My SO makes threats about punishment and discipline but I have never, or at least rarely, seen any of it followed through. I feel i can help, having been raised in a loving but firm family, helping with neices and nephews, and having done varied research of my own. But doing so, i feel we need to be on the same page. I do not want to overstep any boundaries but I cannot continue in this relationship without a change. 

On top of the lack of discipline, my SO is so attached that we go almost nowhere alone. It was one of the agreements we made at the start though that at least one night every few weeks we'd have a date night, just us. Its been almost 2 months since we have done anything. 

I hate myself for feeling this way, but i can't help it. I could really use some advice.