Does paying the value of a document gifted to the giver and donating it as charity absolve one of responsibility and remove any doubt about the permissibility of the act, and is the continuous anxiety suffered by the questioner an obsessive-compulsive disorder?

The religion of Allah is ease, and there is no sin in the document mentioned. These doubts are nothing but whispers from Satan. If you give charity from what you doubt, we hope that it will be an act of piety and a precaution against doubts. The cure for obsessive-compulsive disorder is to turn away from it, ignore it, and occupy oneself with the remembrance of Allah and with what benefits one in this life and the hereafter.