I can't relate any broad-based statistics, only personal experience with a person who left the Organization (twice), married a non-Witness (twice), returned to the Organization (twice), then divorced (twice). I am her second ex-husband. I don't mean to imply anything sinister or bad by saying that, only that the way a person is raised influences how they react in times of stress and difficulty.
He’s quoted a few scriptures and the watchtower a few times, but it constantly sounds like he’s reading from a script with no emotion and no love.
Yes, because as you said, he is literally reading a script. Watchtower, Awake!, meeting talks, Theocratic Ministry School presentations: they are all detailed scripts for how a good Witness is to live their life. Straying from that script for the sake of a "Worldly" (non-Witness) partner can be very stressful for members of the congregation. They often feel they are sacrificing themselves and making major compromises when you think you are agreeing on common ground.
I encourage you to look into the postings about relationships here, and also those at Freeminds. While you do that, try putting yourself into your partner's position: consider how the relationship fits the viewpoint of your Witness partner. It is not impossible to have a successful Witness-Unbeliever relationship, but neither is it an easy thing to do. Please be sure you understand what to expect in this or any other mixed-faith relationship.