Im sorry that your ex is being so difficult - to say the least
What he is doing is making you react, its a way of controlling you and is cruel
from the outside looking in its easier for me to say - stop reacting in the same way that you always react
BUT the game is he has all of October to pay the mortgage or he will find that his credit rating is affected. He is though trying it on with you, knowing that you'll panic.
The hard part is for you to sit back and not worry
You can't make his pay his 50% of the mortgage but you'll have proof you have paid 50% of the mortgage off every payment going forward (if thats what you choose to do) or pay 30% as you always did if thats what happens.
You'll have a note on your credit file showing it was DA that lead to this error in your payments
Does he contact you by email or text? If the latter then text him to state email only going forward and you'll read them once a week on a Monday - and block his number - you don't need the abuse in your hand and can control the emails better, as you don't need to read them more than once a week
legally he can't kick you out of your own home, you have every right to enter the property.