All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
First of all, we appreciate your desire to avoid what is forbidden and your concern not to commit it, and you are right in doing so. We have already clarified how to get rid of unlawful money in Fataawa 87149 and 275392, so please refer to them.
You may get rid of the usury in the manner you mentioned: by giving out the estimated/exact amount of it from your money, because the prohibition is not associated with the money itself, so if you give out the exact amount, it becomes permissible for you to use all the money saved in your account.
Ibn Taymiyyah said in his Fataawa: "The money that is acquired in a forbidden manner, if it is mixed with lawful money, it is obligatory to give out from it (the whole money) the amount of unlawful money, and the amount that remains of the money is lawful to him."
Allaah Knows best.