Why is your cousin carrying the entire load of cleaning - why aren’t you helping?

Okay so she never said she wasn't helping but that aside, I'm utterly fascinated with your disinterest in why he's not helping. I'm also baffled by your assumption that he's "subsidizing" OP's life when he was unemployed for 4 months, time during which he didn't pick up any slack around the apartment. Not to mention the fact that it's not even "his roof" and OP has a job.

Maybe I’m reading the situation wrong

Not only did you read it wrong, you seem to be - I hope accidentally - injecting quite a bit of sexism. You neglect to ask why he isn't helping and place the blame on OP who you had no reason to believe wasn't already doing her fair share of work anyways. You then keep repeating weird things like how she's taking advantage of their generosity and he's "subsidizing" her, incorrectly placing him in the role of "breadwinner" over OP's cousin. It's not 1918, this should not be the position you default to.

Also, what's with this?

He doesn’t sound like a great husband

Way to downplay the escalating abuse. Love it.

She’s probably not going to take your opinion and concern here seriously.

Probably not which is sad. My dad behaved the exact same way right down to the "my roof" commentary and domineering attitude. My mom didn't listen to anyone either. In the end, all she did was piss away her own life.

but you sound biased too

That's not what that word means. When you see actual abuse and decide to finally speak up, that doesn't make you "biased", that makes you "informed" and "caring".