Purim Chronology - Bo 5769

In 12:29, the Pasuk says, (וַיְהִי בַּחֲצִי הַלַּיְלָה). In the song (וַיְהִי בַּחֲצִי הַלַּיְלָה) that is sung on the Seder night, one of the stanzas refers to when Achashveiroish couldn’t sleep, and he called for the Sefer Hazichroinois to be brought before him. So there we also say that the incident occurred on the midnight of the 15^th of Nisan. The problem with this is that the Megillah says B’feirush that the G’zar Din against Klal Yisrael was the 13^th day of Nisan.  Even if that same day Mordechai was there Bil’vush Sak and everything else occurs on that same day, Esther still asks for fasting of 3 days and nights and after that she said she would go into the Melech. So this would be either Tes Zayin or Yud Zayin of Nisan. Now we know the day after Achashveiroish couldn’t sleep, Mordechai was taken on the horse and Haman came home so late that he had to rush to Esther’s party, this would be now the day of Tes Vav Nisan, Pesach itself, according to the song Vayehi Bachatzi Halayloh. This wouldn’t allow for 3 days and nights of fasting before Esther went into the Melech? It is possible that the 3 days started on Yud Gimmel which would make it Tes Vav.