This is a bit confusing to me.
In court, he accused you of taking his money which he had put it in your name in the bank for safe keeping?
If this is the case, you can state in court by showing them the account statement that proves that you didn’t take anything from it.
As for his request that you use this money to spend on yourself and your child, he is only obliged to provide for his son and not for you as you are separated from him. If he wants you to use this money, he has to put it down in writing.
If he had made it a condition that you zero this account so that he would provide for his son, I would suggest that you withdraw all the money and put it in a new account without him knowing this so that you can show him the old account with nothing in it while keeping the new account for the future in case he claims that you had stolen his money.