How can one dispose of usury that may be in money after closing a usurious bank account, given that there are no clear usurious increases in the account statement, and would disposing of 1% of the amount after one year be a suitable solution?

You did well by withdrawing your money from the interest-based bank. If you have not added any interest to your account, you are not required to dispose of any of it, for Allah the Almighty says: "And if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged." If you give any of it as charity, it will be greater for your reward and bring you closer to Allah.