What kind of cancer was he diagnosed with?

Brain tumours sometimes cause personality changes, irritability and mood swings. This was my first thought when reading this.

I am so sorry, babies are incredibly stressful, and the post-partum period is a difficult adjustment. Right now his behaviour is not fair to you or your needs as a partner and a mother. I cannot imagine how exhausted you are mentally and physically. If this is out of character for him, it makes me believe that maybe there's another reason behind it, like perhaps health concerns.

Could you bring up to him that this is something you feel he should get checked out for the sake of your relationship and your family's dynamic? If it's not a tumor would he be open to counselling?

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ETA

I looked through your post history, and saw what the diagnosis of your husband is. I would follow up with an oncologist about this and if the change in behavior is related to his diagnosis.

If it's not it is troubling to me that this side of him is coming out now that you've had a baby. It is stressful but by no means grounds to be abusive or volatile towards your partner and baby. Especially when it seems like you are going above and beyond to make sure you make this as easy for him as possible given the circumstances.

Especially when you are EBF even the most egalitarian couples have an imbalance in roles and responsibilities for babies because you are required to be present or at least pump ahead of time to be able to feed your child. But this is extreme.