If the reality is as you have mentioned, the Waqf is not valid because the house is mortgaged. Moreover, you did not fulfill the
Waqf. You only promised to do so saying: I will assign my share...Etc. Therefore, there is no harm to dispose of it after the redemption by establishing a Waqf or any other legal action. (Part No. 16; Page No. 147) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.