Out of control Lab

Question
My fiance and I recently moved in together (2 months ago). My fiance has a 6 year old male chocolate lab, Samson and I adopted a 3 year old female golden retriever/chow mix (Delilah) shortly after I moved in. Both dogs have been fixed. The introduction of the two dogs went well for the most part. Up until Delilah came along, Samson was the only dog for 6 years, and was "the boss" of the house. My fiance has always encouraged Samson's behavior (chewing on his arm, rough-housing, begging at our meal times, drinking from toilet, sleeping on bed/furniture, etc.). I have been able to correct only two of these behaviors (begging for our food and toilet-drinking). Anyway, Delilah is a very calm dog, and very well behaved. She will play with Samson, but only up to a certain point. Samson gets more and more excited as they play, to a point that seems too aggressive. At that point, Delilah will growl and attempt to leave the play situation and comes to sit by me. Samson does not know when to stop (and rarely listens to my commands). Recently, in the past week, Samson has taken his "playing" up a notch. He chews on Delilah's ears and nips at the fur around her neck. The thing that scars me is that he shows his teeth while engaging in this behavior. Is this just normal "dominance" behavior, or something I should be more concerned with? I don't have much support from my fiance in changing any of Samson's behaviors, as he thinks most of it is funny or not a big deal. I'm inclined to think that Samson is getting jealous of Delilah because her calm behavior gets more rewards than his rambunctious actions but am at a loss as to teaching him how to settle down.
I am concerned not only for Delilah's safety, but we want to have children soon, and I would be very uncomfortable having any children in the house with Samson.

Answer
Samson is highly anxious and has no leadership; your bf's attitude is most likely based on immaturity and perhaps a touch of laziness.  Samson requires behavior modification and positive reinforcement training...BY YOU.  His escalating dominance toward Delilah is a problem, as you realize.  My concern is not only for both dogs, it's for YOU.  You're having CHILDREN with a man who has no regard for your anxiety regarding his dog? You're planning to MARRY someone who exhibits a clear lack of concern for YOUR FEELINGS and is unable, or UNWILLING (even worse) to take responsibility for his dog's behavior?

THINK TWICE, THEN THINK TWICE MORE.  MANY FISH IN THE SEA, little sister.

Meanwhile, go to ClickerTraining.com and learn about positive reinforcement training and USE IT with Samson.  This is a non-coercive method that teaches a dog to VOLUNTARILY perform behaviors (like, "sit", "down", etc., but use different words) for reward.  As the dog learns (one behavior at a time), this method of training promotes the human (YOU) psychologically, demotes the dog psychologically, but provides the dog with behaviors he can perform for reward and praise and provides the human (YOU) with commands to control the dog.  DO NOT tolerate Samson's bullying of Delilah.  Go toward them and "split" them by standing between them and walking very slowly toward Samson, backing him up a foot or two, then walk away.  Do this EVERY TIME Samson's behavior is a visible problem for Delilah.  This indicates to Samson that YOU are "higher ranking" (I hate this dominance conundrum but these terms are necessary at times) and that YOU are intolerant (will NOT tolerate) this sort of behavior.  If necessary, put Samson on an indoor leash (strong but short nylon lead) that you can use to remove him from these situations (without putting hands on him, touch is a primary reinforcer.)  

Now listen to me, and listen well: when a man and woman can't agree on how to TRAIN A DOG, how do you think they will agree on how to RAISE A CHILD? You think you have problems now with the BF and his laissez faire attitude regarding his DOG?  Give this relationship ONE YEAR and your problems will TRIPLE (or worse.)  It doesn't get better, IT ALWAYS GETS WORSE.