In my opinion, your partner has poor coping skills in the face of a certain degree of stress.
When the baby came, he constantly stayed out drinking, thereby neglecting and disrespecting you. While drunk, he thoughtlessly brought his intoxicated friends home.
When I read your thread about his staying out after the baby arrived, I had the impression of an immature, entitled man whose boundaries had weakened. He didn’t want to be home. Although you needed his company, he’d bathe the baby and then head to the pub. If you asked him to stay, he’d say there was no reason for you both to stay in. There were plenty of reasons, but unless you offered sex, he chose to escape.
You finally lowered the boom and asserted your boundaries, and he listened, and I believe he had just begun to stay in with you when this crisis occurred.
He became a financial bully, questioning your purchases and even asking if you really needed a coat, despite earlier declaring the joint account “our money,” and encouraging you to buy whatever you needed.
Then, uncomfortable about your male friend staying over, he felt entitled to rage at you, which terrified you and upset the baby.
He followed the rage by lording financial power, saying he could behave as he wished because he paid the mortgage.
He didn’t apologize the next day. “He didn’t know how to make it right and then he started drinking and was knocking them back.”
You asserted your boundaries by enacting consequences, insisting that he leave while you make decisions.
In summary, he has coped with having a new baby by feeling entitled to neglect and disrespect you, to choose drinking and mates, and to exert financial control. His stress reaction escalated when your friend stayed over, and he selfishly presented rage and increased financial bullying. He chose to drink instead of apologizing immediately.
If you decide to try to work this out, attending couples counseling could greatly benefit you. It would provide a safe space to investigate your communication dynamics and coping strategies. Also, his relationship with alcohol should be addressed.