Does the divorce I swore by to my wife during a fit of extreme anger count, and what is its expiation, especially since I repeated, out of forgetfulness, the words I had sworn to abandon?

As long as you did what you swore not to do out of forgetfulness, and not intentionally, then your oath is not broken, and your divorce does not take effect. This is based on what Al-Nawawi stated in Rawdat al-Talibin: "If the statement or action that was sworn upon occurs due to coercion, forgetfulness, or ignorance, whether the oath was by Allah Almighty or by divorce, does one break the oath? There are two opinions, the most prominent of which is: one does not break the oath." It is obligatory to avoid swearing by divorce, as it is among the oaths of the dissolute, and some scholars have deemed it forbidden.