It is huge.
Okay, so he does a lot of other things for you, but so does the partner of the woman above, and my OH (I have fibro too).
It is hard. It means he has to do more, and it probably puts pressure on him. But he can't behave like this. I'm not sure what the counselling was for, but that would be a warning sign for me...it sounds like the counselling had the short term effect of making him bottle up how he feels, and now it has all come out.
He needs to apologise, and truly mean it. That was a nasty thing to say, and upsetting you when you are in a fibro flare is a horrible thing to do. You are suffering enough, he shouldn't be making that worse. Perhaps reading up on fibro might help too?
But don't feel that because he does things that excuses things. My OH does everything. I can't drive, I have long periods when I can't cook, he makes the bed, brings me medication, gets me drinks, calls me from work when he's there, checks that I'm warm at night, washes my hair, runs the bath, gets me in and out, deals with social services, cleans the house, looks after the pets, goes on chocolate/magazine/biscuit runs...
Men will. Good men will understand that there is nothing you can do, that you are suffering, and want to make that better. He could resent the illness, but not you, and he should never take it out on you. You do all you can.
I dropped the hotpot OH made yesterday. He'd been making it all day. I had a leg spasm and kicked his wine over, he told me he'd sort it, I wanted to make it up to him so tried to replace it and serve tea at the same time - and dropped the whole thing. Ruined. I'm sure he hated me at that second, but he didn't shout. And if he'd said anything half as mean as what your OH said, he'd be gone.
Whatever you decide to do about him, look after yourself. These bad periods suck, and I swear the cold weather doesn't help.