Do the new details about the girl's conversation, her delayed reply, and her subsequent declaration of refusal to marry him, make his initial vow that she would respond to him a vow of disobedience, and therefore can he consider this vow an act of disobedience?

Solving problems is not achieved through repeated vows, but by desisting from them. What was narrated from Al-Adhra'i regarding vows is a matter of dispute even among the Shafi'is themselves, as Zakariya Al-Ansari rejected it and considered it an oversight, supporting this with the Maliki madhhab. The Malikis consider it disliked to make a vow conditional on something other than a sin, and forbidden to make a vow conditional on a sin, though what was named (in the vow) remains binding. Al-Zurqani holds that a vow conditional on a sin is binding. For the questioner, it is permissible to consider this as a vow of sin, and thus be released from it by an expiation for an oath (kaffarat yamin), based on the hadith: "There is no vow in disobedience, and its expiation is the expiation of an oath," and the hadith: "Vows are of two types: what is a vow in obedience to Allah, that is for Allah and must be fulfilled. And what is a vow in disobedience to Allah, that is for Satan and has no fulfillment in it, and it is expiated by what expiates an oath." As for Al-Bujairimi, he holds that if the object of the vow (mandhur) was a sin or permissible, the vow is not contracted. However, if the condition on which the vow was based was a sin or permissible, and it involved urging or prohibiting, or confirming a matter, or attributing something to Allah the Almighty, then it was an oath requiring expiation.