Is it possible to be reassured and act upon the words of Ibn al-Qayyim - may Allah have mercy on him - regarding the one who interprets (his words), and is it permissible to seek fatwas from books of knowledge and use them as an argument for the non-occurrence of divorce for the one who interprets (his words)?

The divorce does not occur due to the absence of the condition upon which it is made contingent. There is no difference whether the intention was merely a threat or to effect a divorce, nor whether the wife was excused or not excused. It is not permissible to rely on books except for proficient researchers and students of knowledge who are able to understand the كلام of the people of knowledge, and to directly refer to the people of knowledge when matters differ in their causes, objectives, time, and place.