As you know yourself by now -- by labeling this money a "bonus" rather than having it as part of the base compensation, the employer can just say, ooops, we can't afford your bonus so you get zip. It's legal. You can do nothing except (1) not factor that money into your family budget because you could see it vanish in a second, or (2) get your husband another job.
Which brings me to what might be the real issue here: You write this at the VERY end of the SWH:
"It's just so frustrating to see people reaching out trying to steal my husband away from this job and have him look the other way and eat up whatever the company he works for dishes out KNOWING full well that he could get something else."
You make a long case for how he could easily get another job that pays more, but you then bury at the end the fact that he will "look the other way" and "eat up whatever the company...dishes out" while he is being actively headhunted by others.
Is there an issue here with his attitude about the job and the fact that maybe while you want him to ditch this job for one where there is more money and it's safer money (i.e. not a "bonus" that can vanish), HE does not want to look for a new job?
It sounds like possibly you and he are not on the same page at all regarding his job and his career. He gets a ton of praise, and could be hired iinstantly, according to you; so what is keeping him from finding these other, easily available, more lucrative jobs? And how mad at him are you over his tendency to just not want to think about changing jobs? Does he feel that your view of his job prospects outside his current job are too rosy and not realistic? Or does he worry that if he leaves this job, any new job might fall apart? Is it possible he fears trying for a new job because (much as he's been told he's fantastic and indispensible at his current job) he secretly worries he might not do well, OR his new employer might screw him, or any of a hundred other worries that might be keeping him where he is rather than out looking for that better-paying job you feel he could have immediately?
What I'm suggesting is...you and he might not be communicating as much as you think you are about this current job, why he remains in it, and what he sees as his prospects if he leaves. He might need some convincing that he could make it in another job; he might need assurance that another employer wouldn't fold under him (I know folks who took great-sounding jobs and the new employers closed within months, so they felt burned forever); he might know things you don't know about his field that worry him and he hasn't shared them with you.
Maybe not. But that last statement about how he is "looking the other way" the earlier statement of yours about how he will "suck it up and sit in...meetings" while just enduring this treatment -- indicate you're mad at him for not getting out there and getting another job. What are you and he going to do to discuss this and find out why you want him out there job-hunting and he doesn't want to do it?
For what it's worth, I'd want my husband out job-hunting in the same situation but I'd want to know what was going on in his head, or in his career field, that was keeping him from doing so.