Cohabitation/breakup/workpermit

My partner and I have been together for 10 years and in Belgium for around 4 - I'm an EU citizen and he (is not) is working here thanks to the fact that we have a legal cohabitation. Things have been tough, and though no breakup is imminent, I cannot help but wonder that its a possibility but I worry that a break up would mean he would have to leave his job + the country. What happens if we break up? Can my partner's company grant a work permit? Would he have to leave Belgium?

Any help would be great!