Couple of observations
If he has worked for this company for a long time, it is incredibly “scary” throwing the towel in proactively and starting again with a new employer. Change is incredibly difficult. Right now he has no sense of a sufficiently burning platform to feel the fear of staying. Hope is an incredibly powerful emotion, so he’s in a more comfortable place hoping it will all turn out ok . I really don’t think that hope will vanish till he is told explicitly that his job is going. Once he knows that the fear of no income will be bigger than fear of starting something new, and he will start to look formwork
second point- do not underestimate how much effort, time etc goes into looking for work. If you’re doing a full days work and want a family life, trying to fit in hunting for a job and the prep work like cv, letter, on line applications , is probably just overwhelming. again without an actual burning platform it may just feel too much for him
Third point: you say he is “emotionally invested”. To many people (and IMHE tends to be more common in men) work is their whole identity. It is what supports their self esteem. If he enjoys it mostly, it is also a source of pleasure . Of course then he’ll be emotionally invested. He’ll be that way with any job he does that he likes and sticks with. It is probably what makes him good at what he does- because he cares. You are sitting on the outside - you are not going to be as invested as this isn’t your work.
I would throw this around the other way. In a partnership you both need to be prepared to switch roles and responsibilities. If you are concerned then start the ball rolling for you now, on how you can step up to bridge the gap if he is made redundant and then needs to start job hunting. Look at how you an increase your salary. Look at how much money would be a shortfall if you cut back on everything else temporarily whilst he is job hunting. Look at what benefits of any may help of he lost his job. Control what you can in meantime.
whilst an ideal person would maybe see the writing on the wall and start looking and even jump a sinking ship, he is not alone in finding that extremely difficult. Hope is an Achilles Heel to many people that makes us continue in a situation long after we should.