* Names have already been changed to protect the fictional.
Michelle wants to know: How are these two going to get along? In my story, they're going to be in love when they meet and marry, but during the next 15 years, will have problems related to accepting one another and modifying some of their own harsher edges. How might this look?
I think everyone who's ever been in a relationship understands the phenomenon of meeting someone and being totally infatuated with the very characteristics that later come to bring resentment, grudges, and discontent. Marriage is no different. We often marry those people who are our opposites, giving credence to the old adage, "opposites attract." The best we can hope for is that there are enough similarities to make up for our differences, enough likemindedness to counteract polar extremes. You as the author will be the only one who knows if Jim and Suzy have what it takes.
You've set up your characters to both have a little bit of the Lion/Choleric personality type, which is good. They'll both probably be direct, which means they won't beat around the bush when it comes to their differences. (Can be good or bad, depending on how they go about the arguments--see below.) Lions actually thrive on opposition, so their differences become something of regular burr under the marriage saddle.
Suzy is a dominant Otter, so she's very people-oriented, which is why her students love her. Jim is dominant Lion, so he's more of a get-'er-done guy with little tolerance for playing around. I'd imagine this would be one of the largest glaring differences between these two personalities. Suzy might get things out of priority in her quest to have fun. Jim might try to take charge of things too much and try to make decisions for Suzy too much to suit her.
You'll have to figure out what the number one pet peeve for Jim is about Suzy and the number one pet peeve for Suzy about Jim. These two hot-topic buttons will be what the other pushes regularly and will most commonly lead to their arguments.
Lucky for you, I've been doing a series of articles for my Thursday Therapeutic Thoughts (T3) for predicting fictional breakups (which, of course, is very much grounded in research about breakups of real people). I think you might find these beneficial, if for no other reason than to see what you might want to steer away from during their arguments if your intent in the book is to have these two stay together. Dr. John Gottman found that there were six signs that, if present, would indicate that a couple was heading for divorce or breakup. I've gone over Signs 1-2, Signs 3-4, and will conclude with signs 5-6 this Thursday.
I'd think it's important to mention that arguing in and of itself isn't an indicator that the relationship is failed. Arguing without the six signs can actually be an indicator of a healthy relationship. No one is going to get along 100% of the time (except, perhaps, during their courtship, when the negatives are not seen through the haze of goo-goo eyes).
You also wanted to know: I'm thinking that something will happen to shake them up, make them realize what they are doing and start looking to God for the answers, instead of just blaming each other. How might this look from a psychological viewpoint?
As I wrote on my post about Lions, "Spiritually, Lions usually need a traumatic experience or event to spur a recognition of a need to make a commitment to Christ." I could also have said that it would take a traumatic experience to end their self-centered focus and gain a heavenly perspective.
And the sky's the limit on traumatic experiences. But I as brainstormed this (with myself), I thought perhaps some trauma involving a child--either them wanting a child, losing a child, having difficulty getting pregnant/getting pregnant/losing that child....something along these lines might be particularly effective. My reasoning would be simply this: realizing that another person depends on their ability to get along might be enough to give them a good shake-up. And it'd be a shake-up experienced together, no mater how you spinned it.
I've often times talked with clients about how there is no one right way to raise a child. The strengths of one parent can offset the weaknesses of the other, and in fact, the child can have an even better upbringing just by having such varied parents. I read a devotional by Nancy Moser in February from Christian Fiction Online Magazine that spoke to this very thing. Read it here.
Hope that this gives you some direction. Personalities are a very fun thing to play around with, using them against one another.