When he blames you for things what is he expecting you to do?
Does he want to get back together or he just moaning?
What do you do when he comes out with the blame nonsense? Difficult though it is, you must not try to defend yourself or justify anything you do or argue. It does not matter. He does not matter. His opinion does not matter. He is no longer your problem. What he says, what he thinks, who cares? Just ignore, ignore, ignore somemore. The only way to win that war is to walk away from battle.
If otoh he wants you back and is playing the can we sort this out, after all it is your fault cards then just agree with him- as in yes I did annoy you, just as well we split up, yes I made your life miserable just as well you are free now etc. Etc.
To be utterly clear though his behaviour is his fault. None of this is your fault. The above are just tactics to deflect him.
Learning not to engage is worth it though as it frees you from him being in anyway your problem. If you do engage don't kick yourself. Just brace yourself to have another go at ignoring him next time. It does get easier.
A friend on EA thread said she used to stare at her ex's forehead and imagine it had a scrolling message on it saying "this is all bollocks. I am a total fuckwit." Etc. As he was droning on.
Don't let him know he has been getting to you. Don't let him know anything about your life. Don't let him cross the threshold.
Boundaries up. Wear them like armour.
Then come here and let it all out.