Is it permissible to demand the relinquishment of the marital apartment or the signing of promissory notes as a condition for the wife's return after the husband's communication with female colleagues was discovered and he repented?

You have done well by repenting from talking to your female colleagues, and beware of returning to that; because talking to a non-mahram (definition) woman without need and without legal Islamic controls is a door to temptation. Your wife spying on your phone is wrong and forbidden. Her family has no right to refuse reconciliation between you or to impose conditions, and if they insist on refusal, refer the matter to the competent authority. Be keen on good relations with in-laws, for Allah has blessed kinship through marriage, and the Sunnah (definition) has enjoined caring for it.