@pallisers hits the nail on the head with their advice;
First of all I wouldn't apologise to someone who treated me like that.
Then if/when he gets over himself calmly sit him down and tell him the very next time he does that to you, you will leave him. That this is your way of dealing with it and it is up to you to decide if it is ok or not.
He holds so much fake power over you because you gave given it to him.
He holds the power to do this because you don't want to not have the children full time - do you really think that it's healthier for your children to grow up with him abandoning them and you like this? Do you really think that he wants sole charge of the children 50% or more of the time? Of course he doesn't, he's not at all interested in raising his kids, he abandons them for a week or more at a time, regularly!
You can't leave him because you don't have anybody to help with childcare - I've got news for you, you are already a single parent with the most flakey of childcare "help" going!
STOP giving him power over you. The sooner you realise that it is HIM who stands to lose (his emotional punchbag, his childcare, his children, his loving wife) and empower yourself to leave him if it suits you, the sooner the power dynamic shifts.
He says it is to protect himself. So he can feel safe
Please understand this - that this refers to his fragile, fragile ego. His ego is so delicate that he is talking about safety from having to face up to the reality that his behaviour is anything less than perfect. That HE is anything less than perfect. He will avoid ever truly considering that his behaviour is in any way bad or wrong, because his identity is too wrapped up in the need to always be right. That's narcissistic personality disorder - I'd bet my bottom dollar he is a narcissist on the purest clinical sense. If so then he cannot change from this. He can learn to pretend to change but he cannot physically ever have the introspection that is needed. Narcissists will destroy those around them - don't walk, RUN away from this. Learn grey rock technique.