Extended logline works a bit better - problem is the term "risk avoiding" - try neurotic, mild-mannered, "scaredy cat", anything really - his risk avoidance can be implied less directly.

Same with "car stalked" which is an odd phrase. Is it important that the stalking is via car? Is it important that he's a ski-instructor?

I'd think -

"While on a holiday to spice up their marriage, a neurotic husband and his straying wife are stalked by her secret admirer (affair partner?). He must act (how? physically? planning? fight? escape? - specifics are better here) to defend his marriage, and his life."

Ski instructor.  

In a bid to save his relationship and at the advice of their marriage counsellor a risk-averse driving instructor takes his wife on a road trip only to discover that they are being stalked by one of her secret admirers.

In a desperate attempt to save his marriage a neurotic driving instructor takes his wife on a roadtrip only to discover their lives are in danger when they are relentlessly pursued by her secret admirer.

...stalked by one of her crazy ex-lovers
find themselves terrorized by

Would help to know what genre this is.
I read it first as Comedy.

One more:
If they're to escape with their lives a straight-laced driving instructor discovers he's going to have to throw the rule-book out the window when he and his adulterous wife are pursued during a road-trip by her crazed lunatic ex-lover.

Or: ... pursued by one of her many secret admirers
Needs a bit of refining. Stakes, goal & urgency are all there.

Welcome to SS.

I was going to comment but LC covered everything I was going to say.

It's like I'm going second in the rap battle against Eminem.

(Mic drop)

Who is Jim?

More times than not, using a character name in a logline is more of a liability than an asset. As you have here. If the name has some historical significance, then it can work in your favor, but yours don't, it only adds words that could be used for something else. So the consensus is not to use character names for your protagonist.  

I don't think it's a hard and fast rule, if it is, then someone correct me. I would scratch Jim and go with driving instructor.

All the best,

Ghost

Agree with Ghost here.

Also, I merged the threads for you so comparisons can be made easily.