One of my pet hates is people who dress up nastiness as "only joking" - be it a literal joke, like this one, that you don't find funny personally, or a more direct snidey remark which, when you object to it, is dismissed as "get a sense of humour" or similar. In other words, it's a devious way of making spite or bullying "acceptable" by pretending it's humour and that any disquiet you feel must be down to your sense of humour failure.
Rubbish. I think in the circumstances described, it's practically gaslighting. Making you think you're imagining any unpleasant intent.
As others have said, context is everything. If your OH was otherwise a good all round bloke then posting a joke like that of questionable taste (yes, Chubby Brown came to my mind too) could be seen as thoughtless rather than an attempt to dig at you - and a good all round bloke would have apologised if you'd told him that you found it objectionable . However, given a significant history of him being nasty, then it seems as if he was goading you OP ..... almost daring you to object ...... whereupon he could then score a "double whammy" by accusing you of being uptight etc (few people like being accused of having no sense of humour) as well as having made the original dig ("hidden" in a "joke").
Yes - no-one else will imagine this "joke" is specifically about you. No-one else will imagine you have a beard. But that's not the point. He sounds a nasty piece of work - and had agreed to be more kind and sensitive recently ....... you might therefore reasonably think that someone who genuinely wanted to be kind would think twice before posting up a "joke" that's pretty misogynistic.
Anyway, "get over yourself" is hardly kind is it ? I suspect you reacted exactly as he'd hoped you would - so he then has a "justifiable" excuse to verbally attack you again.
But having said all that, this "joke" kind of pales into insignificance compared to everything else that's gone on before. I know not everyone splits after the sort of things you described but my god, at the very least, if he valued you and valued your relationship, he would be making huge efforts to be kind as a matter of course - and in recognition of the huge twat he'd been - without the pair of you having to have a conversation about it. It doesn't sound as if he wants to be kind, or sees why he should be kind and pleasant.
Please, as others have suggested, start making plans and seeking advice to get out of this. You'd be no worse off getting legal advice (many solicitors offer cut price initial consultations), general housing and benefits advice from CAB etc.